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Design and Construction of Large-scale Laminar Shear Box for Study of the Behavior of Deep Foundations Subjected to Lateral Loads due to Lateral Spreading using 1-g Shake Table Tests
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen (Supervisor)
Abstract
Using appropriate box as an artificial boundary condition is one of the critical tasks in geotechnical physical modeling of the soil mass especially under cyclic loading such as earthquakes. In general there are two types of boxes which can simulate boundary conditions of scaled models as rigid or flexible conditions. Main purpose of this study is design and construction of a flexible box in a way that effects of boundary condition have been minimized during tests. Construction of this box is the first step of an investigation project which concern to evaluate the effect of lateral spreading as a result of liquefaction on deep foundations of bridges, piers, harbors by using shake table test...
Dry granular flow in a vane shear cell: flow characteristics and rheological laws
, Article Geotechnique ; 2023 ; 00168505 (ISSN) ; Zhang, L ; Mohsen Haeri, S ; Xu, Z ; Sharif University of Technology
ICE Publishing
2023
Abstract
The flow dynamics of dry granular flows is significantly affected by a prominent feature of a granular mass known as dilatancy. Although their rheological behaviour has been characterised via friction and dynamic dilatancy laws, the role of dilatancy in a granular flow has not been much appreciated. In this study, using a vane rheometer, an experimental investigation was conducted on uniform glass beads of (d = 3 mm) at different initial relative densities (15 ≤ Dr ≤ 66%) and shear rates that span over four orders of magnitude. The flow characteristics in terms of effective friction, volume change, and velocity field were obtained and evaluated. The effective friction shows a...
Experimental and Theoretical Investigation of Rheological Behavior of Dry and Saturated Granular Flows
, Ph.D. Dissertation Sharif University of Technology ; Haeri, Mohsen (Supervisor) ; Zhang, Limin (Supervisor)
Abstract
Flow-type landslides, including debris flows, mudflows, and other mass flows, are among the natural hazards triggered by factors such as rainfall or earthquakes. The dynamics of these flows are heavily influenced by the rheological behavior of their constituent mixtures, which encompass a wide range of particle concentrations and sizes. This variability in particle concentration and size significantly alters the rheological behavior of the mixtures. Previous studies have primarily focused on the behavior of equivalent fluids in fine-grained mixtures, often overlooking the role of various interactions and multiphase behavior in coarse-grained mixtures. In this dissertation, the rheological...
Efficiency improvement of a high step up high efficiency converter for photovoltaic applications based on three-state switching cell
, Article PEDSTC 2013 - 4th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2013 , Pages 454-458 ; 9781467344845 (ISBN) ; Zolghadri, M. R ; Hajimoradi, M. R ; Sharif University of Technology
2013
Abstract
This paper suggests methods for improving efficiency of a high step up high efficiency converter based on three state commutation cells. A loss analysis has been performed to identify the source of power loss. Based on this analysis, methods are presented to reduce losses in the most power dissipating elements. These methods include replacing some power diodes with large conduction losses with MOSFETs having small on-state resistance. Efficiency improvement up to %1.25 percent is verified in simulation and experimental results
Rheological behaviour of dilute soil-water mixtures: role of interactions from colloidal and non-colloidal particles
, Article Canadian Geotechnical Journal ; Volume 60, Issue 2 , 2023 , Pages 139-150 ; 00083674 (ISSN) ; Zhang, L. M ; Haeri, S. M ; Xu, Z. D ; Sharif University of Technology
Canadian Science Publishing
2023
Abstract
The rheological behaviour of dilute soil-water mixtures, such as hyperconcentrated mixtures and interstitial fluids in debris flows, can significantly affect the flow dynamics of flow-type landslides. These mixtures often contain clay, silt, and sandy particles. Despite great efforts, the effects of soil type and texture on the rheological behaviour of these mixtures are still not well understood. To tackle this issue, an experimental investigation is carried out using a narrow-gap rotational viscometer to evaluate the interactions from colloidal (clay) and non-colloidal (silt and sand) particles and possibility of flow regime change. The flow curves of dilute mixtures are determined with...
An accurate semi-analytical method for an arbitrarily oriented edge or interior crack in an anisotropic homogeneous elastic solid
, Article European Journal of Mechanics, A/Solids ; Vol. 45 , May , 2014 , pp. 133-142 ; ISSN: 09977538 ; Shodja, H. M ; Sharif University of Technology
2014
Abstract
In this work, a general semi-analytical method for the determination of the elastic fields within an anisotropic homogeneous elastic solid with an inclined edge or interior crack is developed. In this method, the displacement field is represented as a sum of a function and a finite series of functions with unknown coefficients. The functions are constructed in such a way that all the essential homogeneous and inhomogeneous boundary conditions are satisfied exactly and, moreover, the displacement discontinuity across the crack faces as well as the exact singular behaviour of the stress field at the crack-tip are captured. The unknown coefficients are determined by utilizing the principle of...
The scattering of P-waves by a piezoelectric particle with FGPM interfacial layers in a polymer matrix
, Article International Journal of Solids and Structures ; Volume 47, Issue 18-19 , 2010 , Pages 2390-2397 ; 00207683 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2010
Abstract
Propagation of P-wave in an unbounded elastic polymer medium which contains a set of nested concentric spherical piezoelectric inhomogeneities is formulated. The polymer matrix is made of Epoxy and is isotropic; each phase of the inhomogeneity is made of a different piezoelectric material and is radially polarized and has spherical isotropy. Note that the individual phases are homogeneous, and all interfaces are perfectly bonded. The scattered displacement and electric potentials in the matrix are expressed in terms of spherical wave vector functions and Legendre functions, respectively. The transmitted displacement and electric potentials within each phase of the piezoelectric particle are...
Interaction of a screw dislocation and an embedded nonuniformly coated circular fiber with imperfect interfaces
, Article International Journal of Solids and Structures ; Volume 182-183 , 2020 , Pages 295-306 ; Shodja, H. M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The eccentricity between the circular fiber and its coating as well as the imperfection at the fiber-coating-matrix interfaces associated with certain composites can have a remarkable effect on the movement of a dislocation. For an in-depth understanding of such phenomena, the present work provides an exact analytical solution for the interaction between an eccentrically coated circular inhomogeneity embedded in an infinite elastic medium with imperfect interfaces and a screw dislocation. The dislocation may be located inside one of the regions: the core inhomogeneity, coating, or the matrix. The corresponding boundary value problem is solved by using conformal mapping and complex potential...
Evaluation of permeable pavement responses to urban surface runoff
, Article Journal of Environmental Management ; Volume 187 , 2017 , Pages 43-53 ; 03014797 (ISSN) ; Delkash, M ; Tajrishy, M ; Sharif University of Technology
Academic Press
2017
Abstract
The construction of permeable pavement (PP) in sidewalks of urban areas is an alternative low impact development (LID) to control stormwater runoff volume and consequently decrease the discharge of pollutants in receiving water bodies. In this paper, some laboratory experiments were performed to evaluate the efficiency of a PP subjected to sediment loadings during its life span. Simple infiltration models were validated by the laboratory experiments to evaluate the trend and extend of PP infiltration capacity throughout the life of the pavement operation. In addition, performances of the PP in removing total suspended solids (TSS) and selective nutrient pollutants such as NO3 −, NH4 + and...
The scattering of electro-elastic waves by a spherical piezoelectric particle in a polymer matrix
, Article International Journal of Engineering Science ; Volume 44, Issue 10 , 2006 , Pages 633-649 ; 00207225 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2006
Abstract
This paper is devoted to the study of scattering of plane harmonic waves by a piezoelectric sphere with spherical isotropy embedded in an unbounded isotropic polymer matrix. The scattered displacement field and the electric potential in the matrix are expressed in terms of spherical vector wave functions and spherical harmonic functions, respectively. For the field points inside the inhomogeneity, new displacement functions are introduced. Expansion of the new displacement functions and the electric potential in terms of spherical harmonic functions, the equations of motion and electrostatic lead to four second order ordinary differential equations (odes), where three of them are coupled....
A semi-analytical method for piezocomposite structures with arbitrary interfaces
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 194, Issue 42-44 , 2005 , Pages 4588-4604 ; 00457825 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2005
Abstract
A general three-dimensional semi-analytical solution of piezocomposite media consisting of various domains of distinct electro-mechanical properties is proposed. The interfaces between the domains may be non-planar. The geometry and boundary conditions may be arbitrary, and the applied loading can be in the form of traction, displacement, voltage, or any combination of them. In this approach, the unknown displacement field u1, u2, u3, and the electric potential φ are taken as appropriate functions in each domain, such that the continuity of the displacement field and the electric potential are exactly satisfied at the interfaces. Also, the continuities of traction stresses and normal...
Implementing spectral decomposition of time series data in artificial neural networks to predict air pollutant concentrations
, Article Environmental Engineering Science ; Volume 32, Issue 5 , January , 2015 , Pages 379-388 ; 10928758 (ISSN) ; Zare Shahne, M ; Arhami, M ; Sharif University of Technology
Mary Ann Liebert Inc
2015
Abstract
A model to predict air pollutants' concentrations was developed by implementing spectral decomposition of time series data, obtained by Kolmogorov-Zurbenko filter, in Artificial Neural Networks (ANN). This model was utilized to separate and individually predict three spectral components of air pollutants' time series of short, seasonal, and long-term. The best set of input variable was selected by evaluating the significance of different input variables while modeling different time series components. Moreover, different possible approaches for constructing such models were examined. Performance of the constructed model to predict air pollutants' level at a central location in Tehran, Iran,...
A 35 Step Reduced Mechanism for Methane-Air Combustion to Estimate Pollutants
, M.Sc. Thesis Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
A novel reduced mechanism is introduced which aimed to predicts NOx and CO generation in advanced industrial gas turbine combustors. The survey is initially conducted by considering 25 species in GRI-3 mechanism of Methane oxidation and continued to choose nine of the most important species based on the quasi-steady state analysis. Finally, a new skeletal reduced mechanism with 35 reactions and 20 species is derived using sensitivity analysis, reaction path analysis, and some physical reasons. The overall validity of this mechanism is clearly confirmed by comparing the present predicted results with GRI-3 full mechanism in a PSR reactor. The adiabatic flame temperature and all of the main...
Numerical Analysis of Standing Wave Thermoacoustic Nonlinear Processes with Flow Field Investigation
, Ph.D. Dissertation Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
This dissertation investigates and analyzes the nonlinear effects within standing wave thermoacoustic systems. These effects, often overlooked, can play a crucial role in the behavior of such systems. Two-dimensional numerical simulations of the Navier-Stokes equations were conducted using a commercial software, leading to the identification and discovery of new nonlinear physics governing the interaction of heat transfer and hydrodynamic oscillations of fluid particles. The numerical solution method and mesh quality were validated against a similar problem with a well-established numerical solution. Furthermore, a parametric study was performed on a stationary-wave thermoacoustic...
Nonlinear vibration of beams under nonideal boundary conditions
, Article Acta Mechanica ; Volume 218, Issue 3-4 , 2011 , Pages 259-267 ; 00015970 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
In this paper, we investigate the influence of nonideal boundary conditions on the nonlinear vibration of damped Euler-Bernoulli beams subjected to harmonic loads. These nonidealities allow for small deflections and/or moments at the supports of the beam. Using the iteration perturbation method, analytical expressions for the case of simply supported beams with immovable end conditions are provided. The results reveal that the first order of approximation obtained by the proposed method is more accurate than the perturbation solutions. Moreover, compared with the previous studies, some interesting phenomenon is predicted. We have shown that in some special combinations of the nonidealities...
Three-dimensional free vibration of arbitrarily shaped laminated micro-plates with sliding interfaces within couple stress theory
, Article Journal of Sound and Vibration ; Volume 339 , March , 2015 , Pages 176-195 ; 0022460X (ISSN) ; Shodja, H. M ; Forouzan, B ; Sharif University of Technology
Academic Press
2015
Abstract
Free vibration of laminated micro-plates with arbitrary geometry and boundary conditions consisting of several micro-layers with free sliding/frictional sliding/perfect interfaces is of interest. The inter-layer bond in the direction normal to the interfaces is perfect, and thus the corresponding displacement component is continuous across the interfaces. The mentioned in-plane interface conditions may be realized by varying the stiffness of the sliding inter-layer spring of vanishing thickness. For free sliding and perfect interface conditions the stiffness→0 and a, respectively. Couple stress theory as a useful higher order continuum theory is utilized to formulate the problem....
A screw dislocation near a damaged arbitrary inhomogeneity–matrix interface
, Article International Journal of Damage Mechanics ; Volume 29, Issue 2 , 2020 , Pages 272-296 ; Shodja, H. M ; Masoudvaziri, N ; Sharif University of Technology
SAGE Publications Ltd
2020
Abstract
In the literature, the analytical solutions concerned with the interaction between screw dislocation and surfaces/interfaces have been mainly limited to simple geometries and perfect interfaces. The focus of the current work is to provide an approach based on a rigorous semi-analytical theory suitable for treatment of such surfaces/interfaces that concurrently have complex geometry and imperfect bonding. The proposed approach captures the singularity of the elastic fields exactly. A vast variety of the pertinent interaction problems such as dislocation near a multi-inhomogeneity with arbitrary geometry bonded imperfectly to a matrix, dislocation near the free boundaries of a finite elastic...
A piezoelectric medium containing a cylindrical inhomogeneity: Role of electric capacitors and mechanical imperfections
, Article International Journal of Solids and Structures ; Volume 44, Issue 20 , 2007 , Pages 6361-6381 ; 00207683 (ISSN) ; Tabatabaei, S. M ; Kamali, M. T ; Sharif University of Technology
2007
Abstract
Often, during fabrication processes of fiber-matrix composites, the pertinent interface may be made imperfectly bonded either deliberately or undesirably. The effect of electric capacitors and mechanical imperfections on the electro-mechanical fields associated with an anisotropic piezoelectric matrix containing a cylindrical inhomogeneity made of a different anisotropic piezoelectric material is of interest. In fact the interface imperfection condition presented in this paper is quite general, in the sense that any combination of mechanical and electrical imperfections may exist. The interface electrical imperfection is mimicked by the electric capacitors. The capacity of the capacitors is...
A piezoelectric-inhomogeneity system with imperfect interface
, Article International Journal of Engineering Science ; Volume 44, Issue 5-6 , 2006 , Pages 291-311 ; 00207225 (ISSN) ; Tabatabaei, S. M ; Kamali, M. T ; Sharif University of Technology
2006
Abstract
This paper examines the electro-mechanical fields for a circular anisotropic piezoelectric fiber sensor inside an anisotropic piezoelectric or non-piezoelectric elastic matrix with imperfect interface under remote in-plane uniform tension. The interface imperfection is posed on the mechanical fields only. The present formulation admits different boundary value problems in a unified manner, so various fiber-matrix interface conditions are considered: (1) perfect bonding; (2) pure debonding; (3) in-plane pure sliding; (4) out-of-plane pure sliding; (5) full debonding; and (6) partial debonding. An interface condition is modeled by a specific layer of mechanical springs with vanishing...
Controlled islanding for enhancing grid resilience against power system blackout
, Article IEEE Transactions on Power Delivery ; Volume 36, Issue 4 , 2021 , Pages 2386-2396 ; 08858977 (ISSN) ; Amraee, T ; Fotuhi Firuzabad, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
This paper proposes a transient stability constrained controlled islanding (TSC-CI) approach against cascading events in power systems. Using the wide area measurements, the proposed islanding algorithm is implemented regarding the actual dynamic conditions of the resulted islands. Since the main concern, right after the execution of controlled network splitting, is the transient stability of synchronous machines, a transient energy function is utilized for proper network partitioning. The proposed transient stability criterion is expressed as a function of the transfer impedance between each pair of generators in the resulted islands. Transfer impedance between each pair of coherent...