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    Seismic performance and fragility analysis of power distribution concrete poles

    , Article Soil Dynamics and Earthquake Engineering ; Volume 150 , 2021 ; 02677261 (ISSN) Ghahremani Baghmisheh, A ; Mahsuli, M ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    This paper proposes probabilistic damage and collapse models for reinforced concrete poles in electric power distribution networks and investigates the damage and collapse pattern of poles under earthquake excitations. To this end, detailed finite element models of the H-type reinforced concrete poles are developed and verified using past experimental studies as well as the observed damage in previous earthquakes. The models are then subjected to nonlinear static analyses to study the effect of the loading pattern, loading direction, concrete strength, and failure criteria on the capacity and the collapse pattern of the pole. Next, incremental dynamic analysis is carried out to investigate... 

    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... 

    Temperature-Dependent Hierarchical Multi-Scale Modeling of Nano-Materials Considering Surface Effect

    , M.Sc. Thesis Sharif University of Technology Ghahremani, Pegah (Author) ; Khoei, Amir Reza (Supervisor)
    Abstract
    In continuum mechanics, the constitutive models are usually based on the Cauchy-Born (CB) hypothesis which seeks the intrinsic characteristics of the material via the atomistic information and it is valid in small deformation. The main purpose of this thesis is to investigate the temperature effect on the stability and size dependency of Cauchy-Born hypothesis and a novel temperature-dependent multi-scale method is developed to investigate the role of temperature on surface effects in the analysis of nano-scale materials. Three-dimensional temperature-related Cauchy-Born formulation are developed for crystalline structure and the stability and size dependency of temperature-related... 

    A Model for Reducing the Cost of Organization with the Use of Process Attitude (Along with a Case Study)

    , M.Sc. Thesis Sharif University of Technology GHahremani, Amir (Author) ; Eshraghniaye Jahromi, Abdolhamid (Supervisor)
    Abstract
    Undoubtedly, reducing the organization's costs in today's world economy situation is a requisite for the survival of the organization. In order to continue their economic life, organizations must make their movements more effective by reducing costs and increasing agility and productivity. Various methods have been proposed to reduce costs, but before any measurements, identification of the reducible factors is very necessary.
    Improving processes in an organization is considered as one of the best ways to reduce costs and increase profitability. In this research, the goal is to provide a model for reducing costs using process attitude so that the associated costs of the organization can... 

    Quantifying seismic response uncertainty of electrical substation structures using endurance time method

    , Article Structures ; Volume 30 , 2021 , Pages 838-849 ; 23520124 (ISSN) Ghahremani Baghmisheh, A ; Estekanchi, H. E ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    A new procedure is proposed to quantify uncertainties involved in the seismic response of structures including ground motion and modeling variability. The advent of performance-based earthquake engineering (PBEE) and probabilistic seismic risk analysis necessitates consideration of uncertainties in predicting seismic responses. However, the high computational cost of conventional methods restricts their application to only simple numerical models. The present study employs the endurance time (ET) method concept to predict the response distribution which requires much less computational efforts than conventional methods. The proposed procedure for the quantification of record-to-record... 

    Reachability in injective piecewise affine maps

    , Article Proceedings - Symposium on Logic in Computer Science ; Volume 2023-June , 2023 ; 10436871 (ISSN); 979-835033587-3 (ISBN) Ghahremani, F ; Kelmendi, E ; Ouaknine, J ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2023
    Abstract
    One of the most basic, longstanding open problems in the theory of dynamical systems is whether reachability is decidable for one-dimensional piecewise affine maps with two intervals. In this paper we prove that for injective maps, it is decidable.We also study various related problems, in each case either establishing decidability, or showing that they are closely connected to Diophantine properties of certain transcendental numbers, analogous to the positivity problem for linear recurrence sequences. Lastly, we consider topological properties of orbits of one-dimensional piecewise affine maps, not necessarily with two intervals, and negatively answer a question of Bournez, Kurganskyy, and... 

    An analytical investigation of transient imperfectly expanded turbulent jet

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 236, Issue 14 , 2022 , Pages 3057-3063 ; 09544100 (ISSN) Ghahremani, A ; Aramfard, M ; Saidi, M. H ; Sharif University of Technology
    SAGE Publications Ltd  2022
    Abstract
    Supersonic turbulent high-pressure jet flows, which are discharging in low-pressure quiescent ambient, are recognized as imperfectly expanded turbulent jet. Steady-state imperfectly expanded jet flow has been already studied analytically; however, the transient flow has not been thoroughly studied. In the present study, the transient imperfectly expanded jet flow with focus on fuel spray in combustion is investigated analytically employing two-step separation of variables method and Fourier-Bessel expansion. The results are validated using available experimental data. The effects of different parameters such as eddy viscosity and pressure ratio on the behavior of the jet are studied. Results... 

    , M.Sc. Thesis Sharif University of Technology (Author) ; Alvanchi, Amin (Supervisor)
    Abstract
    Limited water resources in Iran have made dams an important part of the country’s infrastructure. As a result of the large number of in-progress and expected dam projects in the country, consideration of sustainability factors during planning, construction and operation phases of dam projects can create significant economical, social and environmental impacts in the long term. To come up with an inclusive sustainable development, new sustainability assessment approaches seek for sustainable development at the entire project’s life-cycle; they are looking for sustainable development at all design, construction, operation, maintenance and even demolition phases. In this research we have... 

    Temperature-dependent multi-scale modeling of surface effects on nano-materials

    , Article Mechanics of Materials ; Volume 46 , March , 2012 , PP. 94–112 Khoei, A. R. (Amir Reza) ; Ghahremani, P ; Sharif University of Technology
    2012
    Abstract
    In this paper, a novel temperature-dependent multi-scale method is developed to investigate the role of temperature on surface effects in the analysis of nano-scale materials. In order to evaluate the temperature effect in the micro-scale (atomic) level, the temperature related Cauchy–Born hypothesis is implemented by employing the Helmholtz free energy, as the energy density of equivalent continua relating to the inter-atomic potential. The multi-scale technique is applied in atomistic level (nano-scale) to exhibit the temperature related characteristics. The first Piola–Kirchhoff stress and tangential stiffness tensor are computed, as the first and second derivatives of the free energy... 

    Identifying Active Followership Behaviors in Interaction with Managers with Autocratic Leadership Style in an Iranian Organization

    , M.Sc. Thesis Sharif University of Technology Ghahremani, Hamed (Author) ; Alavi, Babak (Supervisor) ; Banki, Sara (Supervisor)
    Abstract
    Purpose: The purpose of this thesis was to identify active followership behaviors of followers in interaction with autocratic leaders. An active follower thinks critically and takes initiatives.
    Design: Given that Followership literature is still in its infancy, the research questions needed a qualitative approach, in this case grounded theory. In total, 19 top- & middle-level managers were interviewed as leaders and followers, accordingly, using semi-structured interviews.
    Findings: 4 categories of active followership were found, each having 3-4 specific behaviors. These categories are: precautionary behaviors, facilitating behaviors, modificating behaviors, and consolidating... 

    Dynamic responses of a rectangular plate under motion of an oscillator using a semi-analytical method

    , Article JVC/Journal of Vibration and Control ; Volume 17, Issue 9 , 2011 , Pages 1310-1324 ; 10775463 (ISSN) Ghafoori, E ; Kargarnovin, M. H ; Ghahremani, A. R ; Sharif University of Technology
    2011
    Abstract
    A semi-analytical method is presented to calculate the dynamic responses of a rectangular plate due to a moving oscillator. In previous analytical solutions of the moving oscillator problem, the elastic distributed structure has usually been modeled by an elastic beam structure. This restrictive assumption is removed in this study by assuming a general plate as two-dimensional elastic distributed structure. The method can be applied for any arbitrary path on the plate. A combination of the Fourier and Laplace transformation as well as the convolution theorem is used to solve the governing differential equations of the problem. A modified integration technique is then presented to solve the... 

    Simultaneous analytical solution of the complete system of double-inlet pulse tube refrigerator

    , Article Journal of Thermophysics and Heat Transfer ; Volume 26, Issue 2 , 2012 , Pages 337-344 ; 08878722 (ISSN) Ghahremani, A. R ; Saidi, M. H ; Ebrahimian, M ; Sharif University of Technology
    2012
    Abstract
    Double-inlet pulse tube refrigerators are one of the most common types of cryocoolers. There are several advantages of double-inlet pulse tube refrigerators, such as not having moving parts, reliability, and long life. Double-inlet pulse tube refrigerators have been used in several applications such as cooling the semiconductors, infrared sensors, and astronomical detectors. In the recent decade, several research efforts have been performed to investigate double-inlet pulse tube refrigerators. Generally, most of them are experimental or numerical, and the recent literature survey shows there is not an analytical solution for the complete system of a double-inlet pulse tube refrigerator,... 

    Numerical modeling of pulse tube refrigerator and sensitivity analysis of simulation

    , Article HVAC and R Research ; Volume 19, Issue 3 , 2013 , Pages 242-256 ; 10789669 (ISSN) Jahanbakhshi, R ; Saidi, M. H ; Ghahremani, A. R ; Sharif University of Technology
    2013
    Abstract
    In this article a double-inlet pulse-tube refrigerator (DIPTR) is modeled using the nodal analysis technique. The main complexity of the problem is oscillatory and unsteady characteristics of the flow. Solving the flow field in the regenerator section of the system as a porous medium with nonlocal thermal equilibrium is challenging. Governing equations are developed applying mass, energy, and momentum equations to different finite volumes in each component of DIPTR. A numerical code (SharifPTR), with graphical user interface, has been developed to investigate the influence of geometrical and working parameters on performance. The governing equations are a system of boundary value problems.... 

    A UHF-RFID transceiver with a blocker-canceller feedback and 30 dBm output power

    , Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 60, Issue 11 , 2013 , Pages 3043-3054 ; 15498328 (ISSN) Ghahremani, A ; Rezaei, V. D ; Bakhtiar, M. S ; Sharif University of Technology
    2013
    Abstract
    A single chip UHF-RFID transceiver front-end is presented. The chip was designed according to EPCglobal Class-1 Gen-2 and supports both ETSI and FCC requirements. The receiver front end is capable of rejecting self-jammers as large as 10 dBm with the aid of a feedback loop. The stability and the robustness of the loop and other system requirements are studied. A 30 dBm class-AB power amplifier (PA) with 28% PAE is also integrated on the chip. The pseudo differential architecture of the PA greatly reduces the injection of the signal into the substrate. A simple model is used to estimate the effect of the substrate noise injection by the PA on the receiving circuit modules and design guides... 

    A Framework for Seismic Risk Assessment of Electrical Substation Equipment with Reliability and Endurance Time Methods

    , M.Sc. Thesis Sharif University of Technology Ghahremani Baghmisheh, Amir (Author) ; Esmaeil Purestekanchi, Homayoon (Supervisor)
    Abstract
    Influences of dynmic interaction between substation equipment on responses and fragility are studied. Proposing a framework for seismic risk analysis of substation equipment using reliability and endurance time methods is another aim of this project. Risk, in this contex, means the probability of exceeding monetary loss. Three dimensional models of four vulnerable types of equipment including surge arrester, current transformer, circuit breaker and disconnect switch are developed and verified. Six different systems of equipment connected through rigid bus bars comprising of two, three and four equipment are considered. Fragility curves are developed for equipment in both unconnected and... 

    Design and Implementation of a Front-End For an Integrated UHF-RFID Reader with Tags Direction Finding Ability

    , M.Sc. Thesis Sharif University of Technology Hakamizadeh Ghahremani, Ali (Author) ; Sharif Bakhtiar, Mehrdad (Supervisor)
    Abstract
    Radio Frequency Identification (RFID) is a fast developing research area in the pool of analog RF circuit design. Its applications are growing rapidly, in very different sectors ranging from supply chain management to airport baggage handling or traffic management for non-stop toll collection, etc. RFID surpasses the conventional bar code system in so many fields such as, long read range, multiple tag identification, contactless, re-programmability of tags and no need for a line-of-sight.
    Inthis projecta new approach for modeling and reducing the Multi Path Fading (MPF) error is proposed. It isbased on Direction of Arrival (DOA) technique in thepositioningofpassivetags in UHFRFID... 

    Performance analysis and optimization of high capacity pulse tube refrigerator

    , Article Cryogenics ; Volume 51, Issue 4 , 2011 , Pages 173-179 ; 00112275 (ISSN) Ghahremani, A. R ; Saidi, M. H ; Jahanbakhshi, R ; Roshanghalb, F ; Sharif University of Technology
    2011
    Abstract
    High capacity pulse tube refrigerator (HCPTR) is a new generation of cryocoolers tailored to provide more than 250 W of cooling power at cryogenic temperatures. The most important characteristics of HCPTR when compared to other types of pulse tube refrigerators are a powerful pressure wave generator, and an accurate design. In this paper the influence of geometrical and operating parameters on the performance of a double inlet pulse tube refrigerator (DIPTR) is studied. The model is validated with the existing experimental data. As a result of this optimization, a new configuration of HCPTR is proposed. This configuration provides 335 W at 80 K cold end temperature with a frequency of 50 Hz... 

    Optimization of a regenerative gas turbine engine with isothermal heat addition with the genetic algorithm

    , Article Proceedings of the ASME Turbo Expo, 8 June 2009 through 12 June 2009, Orlando, FL ; Volume 4 , 2009 , Pages 265-274 ; 9780791848852 (ISBN) Haghighi, E ; Borzou, B ; Ghahremani, A. R ; Shafii, M. B ; Sharif University of Technology
    2009
    Abstract
    The use of advanced cycles to take advantage of the gas turbine's thermodynamic characteristics has received increasing attention in recent years. These cycles have been developed for large scale power generation. Due to the powerful abilities of bio-inspired computing techniques such as Genetic Algorithm in locating the optimal (or near optimal) solutions to a given optimization problem, they are widely utilized for determining the parameters of different engineering systems in order to meet the specified performance objectives for a given problem. In order to illustrate the performance of one of these techniques, development and application of it for an engineering problem is presented. In... 

    Optimization of a fed-batch fermenter producing baker's yeast using simulated annealing method

    , Article Iranian Journal of Biotechnology ; Volume 7, Issue 3 , 2009 , Pages 157-165+191 ; 17283043 (ISSN) Ghahremani, H ; Pishvaie, M. R ; Vossoughi, M ; Seyfkordi, A. A ; Sharif University of Technology
    2009
    Abstract
    Modeling of fermentation processes is so complicated and uncertain; therefore it is necessary to provide a robust and appropriate dynamic optimization method. In order to obtain the maximum amount of yeast (Saccharomyces cerevisiae), the bioreactor must be operated under optimal conditions. To determine substrate feeding in a fed-batch bioreactor, a simulated annealing (SA) approach was examined. The optimal glucose feed rate profiles were computed by a stochastic and deterministic problems for various initial conditions to investigate their effects on optimal operation of the fed-batch bioreactor. Results declared a proper capability of SA method for determination of optimal feeding... 

    Acoustic modeling from frequency-domain representations of speech

    , Article Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH, 2 September 2018 through 6 September 2018 ; Volume 2018-September , 2018 , Pages 1596-1600 ; 2308457X (ISSN) Ghahremani, P ; Hadian, H ; Lv, H ; Povey, D ; Khudanpur, S ; Sharif University of Technology
    International Speech Communication Association  2018
    Abstract
    In recent years, different studies have proposed new methods for DNN-based feature extraction and joint acoustic model training and feature learning from raw waveform for large vocabulary speech recognition. However, conventional pre-processed methods such as MFCC and PLP are still preferred in the state-of-the-art speech recognition systems as they are perceived to be more robust. Besides, the raw waveform methods - most of which are based on the time-domain signal - do not significantly outperform the conventional methods. In this paper, we propose a frequency-domain feature-learning layer which can allow acoustic model training directly from the waveform. The main distinctions from...