Loading...
Search for:
rahimi--mahdi
0.118 seconds
Total 770 records
Filtration Based on Electrostatic Devices
, M.Sc. Thesis Sharif University of Technology ; Saidi, Mohammad Said (Supervisor) ; Sani, Mahdi (Supervisor)
Abstract
Particulate air pollution is one of the top environmental health risks. Industrial processes like power generation from fossil fuels and steel and cement manufacturing release a huge amount of particles into the atmosphere. Moreover, internal combustion engines produce a considerable amount of particulate matter in populated areas. The usual way to overcome this risk is using air-cleaning devices such as filters. Filters are designed for specific purposes like removing aerosol particles, aerosol sampling and collecting valuable particles. Because of its diverse applications, filtration has become an active area of research and many kinds of filters are currently available. One type of...
Low Grade Heat Driven Multi-Effect Distillation and Desalination
, Book ; Chua, Hui Tong
Elsevier
2017
Abstract
Low Grade Heat Driven Multi-effect Distillation and Desalination describes the development of advanced multi-effect evaporation technologies that are driven by low grade sensible heat, including process waste heat in refineries, heat rejection from diesel generators or microturbines, and solar and geothermal energy. The technologies discussed can be applied to desalination in remote areas, purifying produced water in oil-and-gas industries, and to re-concentrate process liquor in refineries.
This book is ideal for researchers, engineering scientists, graduate students, and industrial practitioners working in the desalination, petrochemical, and mineral refining sectors, helping them...
This book is ideal for researchers, engineering scientists, graduate students, and industrial practitioners working in the desalination, petrochemical, and mineral refining sectors, helping them...
Analysis and data-based reconstruction of complex nonlinear dynamical systems : using the methods of stochastic processes
, Book
Springer International Publishing
2019
Abstract
This book focuses on a central question in the field of complex systems: Given a fluctuating (in time or space), uni- or multi-variant sequentially measured set of experimental data (even noisy data), how should one analyse non-parametrically the data, assess underlying trends, uncover characteristics of the fluctuations (including diffusion and jump contributions), and construct a stochastic evolution equation?
Here, the term "non-parametrically" exemplifies that all the functions and parameters of the constructed stochastic evolution equation can be determined directly from the measured data.
The book provides an overview of methods that have been developed for the analysis of...
Here, the term "non-parametrically" exemplifies that all the functions and parameters of the constructed stochastic evolution equation can be determined directly from the measured data.
The book provides an overview of methods that have been developed for the analysis of...
Tipping Cascades in Complex Networks: Dynamics and Control
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
Tipping points occur in diverse systems in various disciplines such as ecology, climate science, economy, sociology, and engineering. Critical thresholds in system parameters or state variables at which a tiny perturbation can lead to a qualitative change in the system exist in many subsystems in complex systems. These thresholds are called tipping points, and these subsystems are called tipping elements. Additionally, many systems with tipping points can be modeled as networks of coupled multistable subsystems. Domino-like tippings are called tipping cascades. Considering that these tipping cascades are primarily unprecedented, it is essential to study the dynamics and control of these...
Effects of Higher Order Interactions and Data-Driven Stability Analysis in Tipping Networks
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Rahimi Tabar (Supervisor)
Abstract
Recent studies in various fields such as the environment, climate, economics, and neuroscience have shown that many systems exhibit dynamic responses based on catastrophic shifts—sudden and unexpected changes in the system's state and behavior in response to environmental changes. One of the simplest cases of these shifts occurs when the dynamical bifurcation diagram of a system has a tipping point, which serves as a critical threshold for system parameters, allowing small disturbances to lead to significant changes in the system's state. Research on many natural systems has revealed that tipping elements as the subsystems of a complex system are not independent, and the tipping of one...
Capabilities, difficulties and obstacles for energy recovery from MSW’ as a sustainable option for waste management in Iran
, Article WIT Transactions on Ecology and the Environment ; Vol. 186 , 16-18 December , 2014 , pp. 789-798 ; ISSN: 17433541 ; ISBN: 9781845648374 ; Sharif University of Technology
2014
Abstract
Increasing concerns about unbridled fossil fuel consumption and a growing generation of municipal solid waste (MSW) in Iran and related environmental challenges require adoption of more sustainable approaches in energy and waste management. Energy recovery from waste can play an important role to achieve environmentally sustainable development that has been defined for the country as a main policy. Iran’s growing urban population generates massive amounts of MSW that mostly end up in landfills. A population of 75 million is generating 50,000 tonnes of MSW every day that mostly are buried in landfills. Detrimental emissions from landfills and many other long-lasting environmental issues have...
Mixing performance of T, Y, and oriented Y-micromixers with spatially arranged outlet channel: evaluation with villermaux/dushman test reaction
, Article Microsystem Technologies ; 2016 , Pages 1-14 ; 09467076 (ISSN) ; Azimi, N ; Parsamogadam, M. A ; Rahimi, A ; Masahy, M. M ; Sharif University of Technology
Springer Verlag
2016
Abstract
This study aims to investigate the micromixing performance of three basic types of spatial shaped micromixers. New configurations of T, Y, and oriented Y-spatial mixers were designed with change in the angles of the confluence and the outlet channel to achieve the efficient micromixing. These micromixers offer advantages that are not attainable with the typical types of these mixers. Experimental tests were carried out in the laminar flow regime and the mixing efficiency was evaluated using Villermaux/Dushman test reaction. The geometries of the channels were cylindrical with the length of 30 mm and the diameter of 800 μm. The experimental results show that the angle of outlet channel has a...
Mixing performance of T, Y, and oriented Y-micromixers with spatially arranged outlet channel: evaluation with Villermaux/Dushman test reaction
, Article Microsystem Technologies ; Volume 23, Issue 8 , 2017 , Pages 3117-3130 ; 09467076 (ISSN) ; Azimi, N ; Parsamogadam, M. A ; Rahimi, A ; Masahy, M. M ; Sharif University of Technology
Springer Verlag
2017
Abstract
This study aims to investigate the micromixing performance of three basic types of spatial shaped micromixers. New configurations of T, Y, and oriented Y-spatial mixers were designed with change in the angles of the confluence and the outlet channel to achieve the efficient micromixing. These micromixers offer advantages that are not attainable with the typical types of these mixers. Experimental tests were carried out in the laminar flow regime and the mixing efficiency was evaluated using Villermaux/Dushman test reaction. The geometries of the channels were cylindrical with the length of 30 mm and the diameter of 800 μm. The experimental results show that the angle of outlet channel has a...
MBBR and MBR Reactor Configuration for Better Performance
, M.Sc. Thesis Sharif University of Technology ; Borgheei, Mahdi (Supervisor)
Abstract
Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of...
Forecasting the effects of a Canada-US currency union on output and prices: A counterfactual analysis
, Article Journal of Forecasting ; Volume 32, Issue 7 , 2013 , Pages 639-653 ; 02776693 (ISSN) ; Sharif University of Technology
2013
Abstract
This paper is a counterfactual analysis investigating the consequences of the formation of a currency union for Canada and the USA: whether outputs increase and prices decrease if these countries form a currency union. We use a two-country cointegrated model to conduct the counterfactual analysis, where the conditional forecasts are generated based on the Gaussian assumption. To deal with structural breaks and model uncertainty, conditional forecasts are generated from different models/estimation windows and the model-averaging technique is used to combine the forecasts. We also examine the robustness of our results to parameter uncertainty using the wild bootstrap method. The results show...
Low voltage ride-through capability improvement of DFIG-based wind turbines under unbalanced voltage dips
, Article International Journal of Electrical Power and Energy Systems ; Vol. 60,Issue , 2014 , pp. 82-95 ; ISSN: 01420615 ; Parniani, M ; Sharif University of Technology
2014
Abstract
This paper proposes a competent and effective scheme to enhance the ride-through capability of DFIG-based wind turbines under unbalanced voltage dip conditions. The proposed method is realized through joint use of the rotor-side converter control and a three-phase stator damping resistor (SDR) placed in series with the stator windings. By means of an asymmetrical SDR idea, during the unbalanced voltage dip the SDR resistors are activated only in phase(s) experiencing low voltage. Then, the rotor current is controlled such that no unbalance voltage appears on the stator voltage. The proposed ride-through approach limits the peak values of the rotor inrush current, electromagnetic torque and...
Efficient control scheme of wind turbines with doubly fed induction generators for low-voltage ride-through capability enhancement
, Article IET Renewable Power Generation ; Volume 4, Issue 3 , May , 2010 , Pages 242-252 ; 17521416 (ISSN) ; Parniani, M ; Sharif University of Technology
2010
Abstract
As the penetration of wind power in electrical power systems increases, it is required that wind turbines remain connected to the grid and actively contribute to the system stability during and after grid faults. This study proposes an efficient control strategy to improve the low-voltage ride-through (LVRT) capability in doubly fed induction generators (DFIGs). The proposed scheme consists of passive and active LVRT compensators. The passive compensator is based on a new crowbar arrangement located in series with stator windings. It considerably reduces the rotor inrush current at the instants of occurring and clearing the fault. The active LVRT compensator is realised through rotor voltage...
Dynamic behavior analysis of doubly-fed induction generator wind turbines - The influence of rotor and speed controller parameters
, Article International Journal of Electrical Power and Energy Systems ; Volume 32, Issue 5 , June , 2010 , Pages 464-477 ; 01420615 (ISSN) ; Parniani, M ; Sharif University of Technology
2010
Abstract
This paper analytically investigates the effects of system and controller parameters and operating conditions on the dynamic and transient behavior of wind turbines (WTs) with doubly-fed induction generators (DFIGs) under voltage dips and wind speed fluctuations. Also, it deals with the design considerations regarding rotor and speed controllers. The poorly damped electrical and mechanical modes of the system are identified, and the effects of system parameters, and speed/rotor controllers on these modes are investigated by modal and sensitivity analyses. The results of theoretical studies are verified by time domain simulations. It is found that the dynamic behavior of the DFIG-based WT...
Transient performance improvement of wind turbines with doubly fed induction generators using nonlinear control strategy
, Article IEEE Transactions on Energy Conversion ; Volume 25, Issue 2 , 2010 , Pages 514-525 ; 08858969 (ISSN) ; Parniani, M ; Sharif University of Technology
2010
Abstract
This paper first discusses dynamic characteristics of wind turbines with doubly fed induction generator (DFIG). Rotor back electromotive force (EMF) voltages in DFIG reflect the effects of stator dynamics on rotor current dynamics, and have an important role on rotor inrush current during the generator voltage dip. Compensation of these voltages can improve DFIG ride-through capability and limit the rotor current transients. It is found that the electrical dynamics of the DFIG are in nonminimum phase for certain operating conditions. Also, it is shown that the dynamics of DFIG, under compensation of rotor back EMF and grid voltages, behave as a partially linearizable system containing...
Grid-fault ride-through analysis and control of wind turbines with doubly fed induction generators
, Article Electric Power Systems Research ; Volume 80, Issue 2 , February , 2010 , Pages 184-195 ; 03787796 (ISSN) ; Parniani, M ; Sharif University of Technology
2010
Abstract
This paper deals with the low voltage ride-through (LVRT) control of wind turbines with doubly fed induction generators (DFIGs) under symmetrical voltage dips. The investigation first develops a mathematical formula for the rotor current and rotor voltage when DFIG is subjected to a symmetrical voltage dip. From the analysis, the reasons of rotor inrush current and factors influencing it are inferred. Then, a control scheme enhancing the wind turbine LVRT capability is designed and simulated. The proposed control scheme consists of a nonlinear control strategy applied to the rotor-side converter and a dc-link voltage control applied to the grid-side converter. It improves the damping of DFIG...
Coordinated control approaches for low-voltage ride-through enhancement in wind turbines with doubly fed induction generators
, Article IEEE Transactions on Energy Conversion ; Volume 25, Issue 3 , 2010 , Pages 873-883 ; 08858969 (ISSN) ; Parniani, M ; Sharif University of Technology
2010
Abstract
This paper deals with the coordinated control of rotor- and grid-side converters in wind turbines with doubly fed induction generators (DFIGs) to improve the low-voltage ride-through capability. The rotor-side converter control and additional equipment, called stator damping resistor, are used to limit the rotor inrush current and to reduce the oscillations and settling time of DFIG transient response during the voltage dip. Also, the grid-side converter is controlled to limit the dc-link overvoltage during the voltage drop. It is found that the dynamics of the grid-side converter and dc-link voltage exhibit nonminimum phase behavior, and thus there is an inherent limitation on the...
Removal of toxic metal ions from sungun acid rock drainage using mordenite zeolite, graphene nanosheets, and a novel metal–organic framework
, Article Mine Water and the Environment ; Volume 35, Issue 1 , 2016 , Pages 18-28 ; 10259112 (ISSN) ; Mohaghegh, N ; Sharif University of Technology
Springer Verlag
2016
Abstract
We evaluated the sorptive properties of mordenite zeolite (MOR), a copper terephthalate metal–organic framework (MOF), and graphene oxide (GO) and their potential use in treating acid rock drainage (ARD) containing Fe3+, Cu2+, Mn2+, Zn2+, Pb2+, and Cd2+ ions. MOR was prepared via a hydrothermal method, MOF was prepared via a solvothermal method, and few-layered GO nanosheets were synthesized using Hummers’ method. The aqueous contaminants were removed by chemico-physical sorption and ion exchange in batch tests. It proved possible to dramatically improve removal efficiency and sorptive capacity by optimizing experimental conditions. Magnetic MOF crystals were more efficient in removing...
Dynamic behavior and transient stability analysis of fixed speed wind turbines
, Article Renewable Energy ; Volume 34, Issue 12 , 2009 , Pages 2613-2624 ; 09601481 (ISSN) ; Parniani, M ; Sharif University of Technology
2009
Abstract
This paper analytically investigates the dynamic behavior of fixed speed wind turbines (FSWTs) under wind speed fluctuations and system disturbances, and identifies the nature of transient instability and system variables involved in the instability. The nature of transient instability in FSWT is not similar to synchronous generators in which the cause of instability is rotor angle instability. In this paper, the study of dynamic behavior includes modal and sensitivity analysis, dynamic behavior analysis under wind speed fluctuation, eigenvalue tracking, and using it to characterize the instability mode, and investigating possible outcomes of instability. The results of theoretical studies...
Structural reliability approach to analysis of probabilistic seismic hazard and its sensitivities
, Article Bulletin of Earthquake Engineering ; Volume 17, Issue 3 , 2019 , Pages 1331-1359 ; 1570761X (ISSN) ; Mahsuli, M ; Sharif University of Technology
Springer Netherlands
2019
Abstract
This paper presents a new probabilistic framework for seismic hazard assessment and hazard sensitivity analysis. Hazard in this context means the probability of exceeding a measure of ground shaking intensity, such as peak ground acceleration and spectral acceleration. The main components of the proposed framework include structural reliability methods to estimate exceedance probabilities and their sensitivities, and multiple probabilistic models for earthquake occurrence, magnitude, location, and ground motion. This paper presents two analysis approaches. The first approach utilizes the first- and second-order reliability methods and importance sampling. This approach efficiently yields the...
New hybrid nanocomposite of copper terephthalate MOF-graphene oxide: synthesis, characterization and application as adsorbents for toxic metal ion removal from Sungun acid mine drainage
, Article Environmental Science and Pollution Research ; Volume 24, Issue 28 , 2017 , Pages 22353-22360 ; 09441344 (ISSN) ; Mohaghegh, N ; Sharif University of Technology
2017
Abstract
The application of a hybrid Cu(tpa).GO (Cu(tpa) copper terephthalate metal organic framework, GO graphene oxide) composite as a new adsorbent for the removal of toxic metal ions was reported. New hybrid nanocomposite with excellent dispersibility and stability was successfully fabricated by the simple and effective ultrasonication method. The synthesized composite was characterized by scanning electron microscopy (SEM), UV-Vis and Fourier-transform infrared (FT-IR) techniques. The characterization results concluded that the binding mechanism of the Cu(tpa) and GO was related to both packing and hydrogen bonding. For scrutinizing the sorption activity, the prepared adsorbents were assessed...