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inverse-modeling
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Semi-active vibration control of an eleven degrees of freedom suspension system using neuro inverse model of magnetorheological dampers
, Article Journal of Mechanical Science and Technology ; Volume 26, Issue 8 , 2012 , Pages 2459-2467 ; 1738494X (ISSN) ; Abbasi, M ; Mahdavi, H ; Osgouie, K. G ; Sharif University of Technology
Springer
2012
Abstract
A semi-active controller-based neural network for a suspension system with magnetorheological (MR) dampers is presented and evaluated. An inverse neural network model (NIMR) is constructed to replicate the inverse dynamics of the MR damper. The typical control strategies are linear quadratic regulator (LQR) and linear quadratic gaussian (LQG) controllers with a clipped optimal control algorithm, while inherent time-delay and non-linear properties of MR damper lie in these strategies. LQR part of LQG controller is also designed to produce the optimal control force. The LQG controller and the NIMR models are linked to control the system. The effectiveness of the NIMR is illustrated and...
Experimental and Modeling Study of Two-Phase Relative Permeability at Near Miscible Condition
, M.Sc. Thesis Sharif University of Technology ; Masihi, Mohsen (Supervisor) ; Ghazanfari, Mohammad Hossein (Supervisor) ; Rasaei, Mohammad Reza (Supervisor)
Abstract
One of the main parameters in modeling of two phase gas and oil flow is an accurate relative permeability functions. This importance will be more intensified when the miscibility condition approaches. In miscible condition due to reduction of interfacial tension between oil and gas phases, parameters of conventional relative permeability functions will change and this changing affects on production results such as oil and gas recovery and also pressure drop along the core. All of the previous studies could not present a unique and consistent model to show the effect of near miscibility condition on relative permeability curves. In this work, these changing of parameters will be investigated...
Experimental investigation of near miscibility effect on relative permeability curves
, Article 74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources, 4 June 2012 through 7 June 2012 ; June , 2012 , Pages 5469-5474 ; 9781629937908 (ISBN) ; Masihi, M ; Ghazanfari, M. H ; Sharif University of Technology
European Association of Geoscientists and Engineers, EAGE
2012
Abstract
The requirement of reliable relative permeability data is more intensified when the miscibility condition approaches. In this work the relative permeability of CO2 and oil has been measured at different miscibility conditions using conventional methods. Fractured dolomite and sandstone core plugs samples were used in the experiments. Due to some errorful assumptions of conventional methods such as immiscible, incompressible displacement, inverse modeling was used for predicting the reliable relative permeability of oil and gas phases at near miscible condition from measured oil production and pressure drop data. The initial guesses of relative permeabilities were provided from conventional...
Uncertainty Analysis and Inverse Modeling of Seawater Intrusion in Coastal Aquifers
, Ph.D. Dissertation Sharif University of Technology ; Ataei Ashtiani, Behzad (Supervisor)
Abstract
Groundwater is the primary source of freshwater in many coastal areas and small islands around the world. The most important hazard to groundwater quality in coastal aquifers is seawater intrusion (SWI) resulting from over pumping, prolonged drought conditions and sea level rise due to climate change impacts. Numerical models of SWI are an important tool in the management of coastal aquifers. However, numerical modeling of SWI is one of the most challenging problems in groundwater hydrology. One of the reasons for the challenging nature of SWI numerical modeling is the relatively large level of uncertainty associated with the estimation of the model input parameters. This study focused on...
Thermodynamic Analysis of the Temporal Changes in Salt Concentration in Saline Lakes (the case of Urmia lake)
, M.Sc. Thesis Sharif University of Technology ; Tajrishi, Masoud (Supervisor)
Abstract
Urmia Lake is a strong electrolyte containing various salts, with a thermodynamic identity. Changes in the temperature and volume of lake water cause a change in the concentration of ions in this brine as well as the composition and precipitation of salts in the lake. As a result of these changes, the thermodynamic properties of brine are also changed. The purpose of this study was to investigate the effect of mixing the rivers entering the lake and calculate and analyze the changes in the quality and hydrogeochemical characteristics of Urmia Lake and the amount of precipitation and dissolution of the main minerals in Urmia Lake during the period of 2007-2013 per month. For this purpose,...
Three Dimensional Numerical Simulation of Fresh Water Lens in Small Islands (Case Study: Kish Island)
, M.Sc. Thesis Sharif University of Technology ; Ataei Ashtiani, Behzad (Supervisor)
Abstract
Sensitive ecosystem and scarcity of freshwater are the main characteristics of small islands. These islands have small catchments and usually lack tangible surface water resources. As a result these islands are dependent almost entirely on groundwater. Groundwater on small islands usually occurs in the form of a freshwater lens floating on the more dense saline water. The freshwater lens is highly sensitive to various stresses such as drought, pumping, sea tide, etc. Due to the importance of freshwater lens in islands, proper and optimal use of this vital resource should be studied. Kish island`s freshwater lens was three dimensionally simulated using the numerical model SUTRA. The aim was...
Position control of shape memory alloy actuator based on the generalized Prandtl-Ishlinskii inverse model
, Article Mechatronics ; Volume 22, Issue 7 , 2012 , Pages 945-957 ; 09574158 (ISSN) ; Zakerzadeh, M. R ; Sharif University of Technology
2012
Abstract
Hysteresis and significant nonlinearities in the behavior of Shape Memory Alloy (SMA) actuators encumber effective utilization of these actuator. Due to these effects, the position control of SMA actuators has been a great challenge in recent years. Literature review of the research conducted in this area shows that using the inverse of the phenomenological hysteresis models can compensate the hysteresis of these actuators effectively. But, inverting some of these models, such as Preisach model, is numerically a complex task. However, the generalized Prandtl-Ishlinskii model is analytically invertible, and therefore can be implemented conveniently as a feedforward controller for compensating...
Adjoint Inverse Modeling of PM2.5 Emissions in Order to Improve Performance of Air Quality Models
, Ph.D. Dissertation Sharif University of Technology ; Hosseini, Vahid (Supervisor) ; Mozafari, Ali Asghar (Supervisor)
Abstract
In atmospheric studies, chemical transport models are formulated to simulate the spatial and temporal distribution of pollutant concentrations. However, the performance of these models is strongly dependent on the input parameters such as emissions. Inverse modeling is a widely used mathematical approach for estimating model parameters by minimizing the discrepancy between model output and observations. For air quality studies, inverse modeling is often used for emission inversion as emissions are associated with significant amount of uncertainties.This research aims to estimate optimal values for anthropogenic PM2.5 emission through a four-dimensional variational (4D-Var) inverse modeling...
Inverse modelling for freshwater lens in small islands: Kish Island, Persian Gulf
, Article Hydrological Processes ; Volume 27, Issue 19 , 2013 , Pages 2759-2773 ; 08856087 (ISSN) ; Rajabi, M. M ; Ketabchi, H ; Sharif University of Technology
2013
Abstract
A number of challenges including instability, nonconvergence, nonuniqueness, nonoptimality, and lack of a general guideline for inverse modelling have limited the application of automatic calibration by generic inversion codes in solving the saltwater intrusion problem in real-world cases. A systematic parameter selection procedure for the selection of a small number of independent parameters is applied to a real case of saltwater intrusion in a small island aquifer system in the semiarid region of the Persian Gulf. The methodology aims at reducing parameter nonuniqueness and uncertainty and the time spent on inverse modelling computations. Subsequent to the automatic calibration of the...
A mathematical and experimental analysis of role of ultrasonic wave radiation on relative permeabilties in gravity drain
, Article 73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011 ; Volume 7 , May , 2011 , Pages 5104-5108 ; 9781617829666 (ISBN) ; Keshavarzi, B ; Ghazanfari, M ; Ghotbi, C ; Amani, M ; Sharif University of Technology
Society of Petroleum Engineers
2011
Abstract
This work concerns with experimental and analytical investigation of role of ultrasonic wave radiation in relative permeability of both wetting and non-wetting phases in a free gravity drainage process in porous media under the influence of ultrasonic wave. Glass beads ranged from 70 to 100 mesh sizes were packed and used in the tests. The working fluids consist of distilled water, kerosene and Doroud and Paidar crude oils as wetting and air as non-wetting phase. The measured oil recovery data along with Hagoort (1984) backward methodology were used to determine and to compare the relative permeability of wetting phases in presence and absence of ultrasonic radiation. In addition, the...
Neural networks control of autonomous underwater vehicle
, Article ICMEE 2010 - 2010 2nd International Conference on Mechanical and Electronics Engineering, Proceedings, 1 August 2010 through 3 August 2010 ; Volume 2 , August , 2010 , Pages V2117-V2121 ; 9781424474806 (ISBN) ; Khayyat, A. A ; Ghaemi Osgouie, K ; Sharif University of Technology
2010
Abstract
This paper describes a neural network controller for autonomous underwater vehicles (AUVs). The designed online multilayer perceptron neural network (OMLPNN) calculates forces and moments in earth fixed frame to eliminate the tracking errors of AUVs whose dynamics are highly nonlinear and time varying. Another OMLPNN has been designed to generate an inverse model of AUV, which determine the appropriate propeller's speed and control surfaces' angles receiving the forces and moments in the body fixed frame. The designed approximation based neural network controller with the use of the backpropagation learning algorithm has advantages and robustness to control the highly nonlinear dynamics of...
Transparency enhancement of haptic systems based on compensation of device dynamics
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009 ; Volume 10, Issue PART A , 2010 , Pages 103-110 ; 9780791843833 (ISBN) ; Ahmadian, M. T ; Vossoughi, G. R ; Motamedi, M ; Sharif University of Technology
Abstract
Transparency is a measure of performance in haptic devices. In order to improve transparency and reduce the difference between the impedance transmitted to the user and the target impedance it is necessary to compensate for the dynamics of the haptic device. Due to stability reasons improvement of transparency is limited. Passivity as a stability criterion has been used widely in design and analysis of haptic devices, Since passivity is a conservative criterion, it acts as an obstacle in improving transparency of the haptic interfaces. In this paper instead of passivity, robust stability of the interaction is studied in the presence of parametric uncertainties due to variations in user hand...
A new hybrid inverse modeling method for water quality monitoring using remotely sensed data
, Article SPE Saudi Arabia Section Technical Symposium 2007, 7 May 2007 through 8 May 2007 ; 2007 ; 9781555639600 (ISBN) ; Schaale, M ; Shouraki, S. B ; Fell, F ; Fischer, J ; Taheri, M ; Preusker, R ; Tajrishy, M ; Vatandoust, M ; Shahraeini, M. T ; Sani, P.N ; Taherishahraini, Z ; Khodaparast, H ; Sharif University of Technology
Society of Petroleum Engineers
2007
Abstract
All of the man-made objects and anthropogenic activities related to the oil industries in water bodies (e.g. drilling, equipment installation, construction of oil platfonns and especially oil spillages) have enviromnental impacts on water ecosystems. The assessment of oil field operations and oil platfonns impacts on water quality have become a necessity throughout the world. Phytoplanktons have the lowest trophic level in water enviromnent; therefore the life of all of the other marine animals is highly relevant to phytoplanktonic population. Hence it seems necessary to monitor the spatiotemporal effects of different activities and events, related to oil industries on phytoplanktons....
An innovative inverse analysis based on the Bayesian inference for concrete material
, Article Ultrasonics ; Volume 124 , 2022 ; 0041624X (ISSN) ; Toufigh, V ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Nondestructive tests and evaluations are robust techniques for inspecting different attributes of concrete configuration. However, most nondestructive techniques focused on an aspect of concrete configuration based on comparison to other samples. In this paper, an innovative inverse analysis technique was developed to inspect different attributes of concrete configuration simultaneously. The methodology was based on the scattering feature of the ultrasonic waves during propagation in heterogeneous media. The transition matrix method was employed to determine the scattered wavefield. This method considers the shape of objects, unlike most other numerical methods. Furthermore, a novel...
A mathematical analysis of the mechanism of ultrasonic induced fluid percolation in porous media: Part I
, Article Proceedings - SPE Annual Technical Conference and Exhibition, 20 September 2010 through 22 September 2010 ; Volume 7 , September , 2010 , Pages 5833-5856 ; 9781617389641 (ISBN) ; Sharif University of Technology
2010
Abstract
This work concerns with experimentally and analytically investigation of free gravity drainage process in porous media under the influence of ultrasonic wave radiation. Glass beads ranges from 70 to 100 mesh sizes were packed and used in the tests. The working fluids consist of distilled water, kerosene and Doroud and Paidar crude oils as wetting and air as non-wetting phase. The measured oil recovery data along with Hagoort (1984) backward methodology were used to determine and to compare the relative permeability of wetting phases in presence and absence of ultrasonic radiation. In addition the relative permeability of non-wetting phases for both cases were calculated from inverse modeling...