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Generalized equivalent circuit model for analysis of graphene/metal-based plasmonic metasurfaces using Floquet expansion
, Article Optics Express ; Volume 30, Issue 20 , 2022 , Pages 35486-35499 ; 10944087 (ISSN) ; Memarian, M ; Khavasi, A ; Sharif University of Technology
Optica Publishing Group (formerly OSA)
2022
Abstract
Due to the wide range of applications of metal/graphene-based plasmonic metasurfaces (sensors, absorbers, polarizers), it has become essential to provide an analytical method for modeling these structures. An analytical solution simplified into a circuit model, in addition to greatly reducing the simulation time, can become an essential tool for designing and predicting the behaviors of these structures. This paper presents a high-precision equivalent circuit model to study these structures in one-dimensional and two-dimensional periodic arrays. In the developed model, metallic patches similar to graphene patches are modeled as surface conductivity and with the help of current modes induced...
Drilled shafts in sand: failure pattern and tip resistance using numerical and analytical approaches
, Article International Journal of Geotechnical Engineering ; Volume 16, Issue 8 , 2022 , Pages 974-990 ; 19386362 (ISSN) ; Ahmadi, M. M ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
Drilled shafts are one of the most important types of pile foundations. Several researchers have suggested different soil failure patterns for driven piles; however, for drilled shafts, this issue is inadequately addressed in the literature. In this paper, a numerical approach was pursued to obtain the location and dimensions of plastic zones around the tip of drilled shafts. The dependence of the suggested failure pattern size on the soil properties and drilled shaft dimensions was investigated. Based on several analyses, a soil jug-shaped failure pattern around the tip of drilled shafts was proposed, and its dimensions were determined using the regression-based and trial and error...
Dynamic analysis of electrorheological fluid sandwich cylindrical shells with functionally graded face sheets using a semi-analytical approach
, Article Composite Structures ; Volume 295 , 2022 ; 02638223 (ISSN) ; Haddadpour, H ; Shakhesi, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The present research is performed to calculate the natural frequencies, loss factors, and associated mode shapes of a sandwich cylinder with moderately thick functionally graded (FG) face sheets and an electrorheological (ER) fluid core. Each face sheet is assumed to be made of FG materials, and its displacement field is estimated based on the first-order shear deformation theory, like the ER constrained layer. A suitable displacement continuity condition is considered between layers. The ER fluid used in the central middle is analyzed in the pre-yield area and considered electric field dependent. Hamilton's principle is used to acquire the motion equations related to each layer and...
Nonlinear Elastic Analysis of FG Arcs under Thermo-Mechanical Loading
, M.Sc. Thesis Sharif University of Technology ; Fallah, Famida (Supervisor)
Abstract
Arcs and rings are used extensively in structures such as submarines and bridges due to their particular geometry. On the other hand, in multi-part rocket, due to the high temperature gradients, they form the fastening rings of functional materials (FGM). Considering the importance of this structural element, in this thesis, linear and nonlinear behavior (including bending and post-buckling) of rings made of functionally graded materials under different types of thermo-mechanical loading has been investigated. First, the governing equations are derived from the principle of minimum potential energy, based on the two theorems of Donnell and Love. Donnell's theory equations are solved...
Reliability and Economic Evaluation of Power System with Wind Power
, M.Sc. Thesis Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor)
Abstract
The demand for electrical energy is increasing. The main source of energy at this moment is fossil fuels. High price, great amount of pollution, uneven distribution and global warming are major disadvantages of fossil fuels. Using renewable resources can tackle these issues. Hence, the demand for renewable energy are highly increased. The wind energy is one type of renewable energy. Increasing the wind power penetration impairs the functionality of power system and causes the environmental issues. In order to have a stable power system this effect should be investigated thoroughly. Due to the inherent uncertain characteristics of wind energy, it is desirable to determine the characteristics...
Bubble in flow field: A new experimental protocol for investigating dynamic adsorption layers by using capillary pressure tensiometry
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Vol. 460, issue , 2014 , p. 369-376 ; Bastani, D ; Ulaganathan, V ; Miller, R ; Javadi, A ; Sharif University of Technology
Abstract
For many years the model of a dynamic adsorption layer (DAL) is well established as explanation for the behavior of rising bubbles in surfactant solutions. This model explains the velocity profile and the evolution of the shape of a rising bubble based on the hypothesis of the balance between the drag force and the structure of the adsorbed layer governed by Marangoni convection. However, direct measurements of interfacial properties of the bubble during rising are a real challenge. Here we present a new experimental protocol called "bubble in flow field" suitable for direct measurements of dynamic interfacial properties of a bubble surface using the capillary pressure tensiometry under...
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
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...
Unsupported advance length in tunnels constructed using New Austrian Tunnelling Method and ground surface settlement
, Article International Journal for Numerical and Analytical Methods in Geomechanics ; Volume 37, Issue 14 , 2013 , Pages 2170-2185 ; 03639061 (ISSN) ; Ahmadi, M. M ; Hajjar, M ; Kashighandi, A ; Sharif University of Technology
2013
Abstract
Tunnels constructed using New Austrian Tunnelling Method (NATM) are always based on certain round (unsupported) advance lengths, after which, the temporary lining is placed. The settlement of the ground surface resulting from such construction is of high significance in design and practice. The existing data in this respect, however, is scarce. It is the aim of this paper to propose a semi-analytical procedure based on three-dimensional finite element analyses to predict the maximum surface settlement of the ground in NATM tunnels under different combinations of tunnel diameter, overburden depth, round length and soil and lining properties. The comparison of the results with three case...
Semi-analytical solution for the free vibration analysis of generally laminated composite Timoshenko beams with single delamination
, Article Composites Part B: Engineering ; Volume 45, Issue 1 , 2013 , Pages 587-600 ; 13598368 (ISSN) ; Ahmadian, M. T ; Jafari Talookolaei, R. A ; Abedi, M ; Sharif University of Technology
2013
Abstract
A rather new semi-analytical method towards investigating the free vibration analysis of generally laminated composite beam (LCB) with a delamination is presented. For the first time the combined effects of material couplings (bending-tension, bending-twist, and tension-twist couplings) with the effects of shear deformation, rotary inertia and Poisson's effect are taken into account. The semi-analytical solution for the natural frequencies and mode shapes are presented by incorporating the constraint conditions using the method of Lagrange multipliers. To verify the validity and the accuracy of the obtained results, they were compared with the results from other available references. Very...
Impact of stripe unit size on performance and endurance of SSD-based RAID arrays
, Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 1978-1998 ; 10263098 (ISSN) ; Asadi, H ; GhasemiGol, M ; Sharif University of Technology
Sharif University of Technology
2013
Abstract
Over the past decades, Redundant Array of Independent Disks (RAIDs) have been configured based on mechanical characteristics of Hard Disk Drives (HDDs). With the advent of Solid-State Drives (SSDs), configurations such as stripe unit size can be far from the characteristics of SSDs. In this paper, we investigate the effect of stripe unit size on the endurance and the overall I/O performance of an SSD-based RAID array and compare the optimal stripe unit size with the suggested stripe unit sizes for HDD-based RAID. To this end, we first examine the number of extra page reads and writes imposed by write requests, and then observe the corresponding impact on the overall throughput and the...
Use of PSO in parameter estimation of robot dynamics; part one: No need for parameterization
, Article 2012 16th International Conference on System Theory, Control and Computing, ICSTCC 2012 - Joint Conference Proceedings ; 2012 ; 9786068348483 (ISBN) ; Namvar, M ; Sharif University of Technology
2012
Abstract
Offline procedures for estimating parameters of robot dynamics are practically based on the parameterized inverse dynamic model. In this paper, we present a novel approach to parameter estimation of robot dynamics which removes the necessity of parameterization (i.e. finding the minimum number of parameters from which the dynamics can be calculated through a linear model with respect to these parameters). This offline approach is based on a simple and powerful swarm intelligence tool: the particle swarm optimization (PSO). In this paper, we discuss and validate the method through simulated experiments. In "Part Two" we analyze our method in terms of robustness and compare it to robust...
Introducing a distributed model of the heart
, Article Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics, 24 June 2012 through 27 June 2012 ; June , 2012 , Pages 419-424 ; 21551774 (ISSN) ; 9781457711992 (ISBN) ; Jahed, M ; Sharif University of Technology
2012
Abstract
Conventional models of cardiovascular system (CV) frequently lack required detail. Once utilized to study the heart function, these models focus primarily on the overall relationship between pressure, flow and volume. This study proposes a localized and regional model of the CV system. It utilizes non-invasive blood flow and pressure seed data and temporal cardiac muscle regional activation to predict the operation of the heart. Proposed localized analysis considers specific regions of the heart, namely base, mid and apex sections of the left ventricle. This modular system is based on a hydraulic electric analogy model, estimating desired parameters, namely resistance (R), compliance (C),...
Modelling plastic scintillator response to gamma rays using light transport incorporated FLUKA code
, Article Applied Radiation and Isotopes ; Volume 70, Issue 5 , May , 2012 , Pages 864-867 ; 09698043 (ISSN) ; Etaati, G. R ; Ghal Eh, N ; Safari, M. J ; Afarideh, H ; Asadi, E ; Sharif University of Technology
2012
Abstract
The response function of NE102 plastic scintillator to gamma rays has been simulated using a joint FLUKA+PHOTRACK Monte Carlo code. The multi-purpose particle transport code, FLUKA, has been responsible for gamma transport whilst the light transport code, PHOTRACK, has simulated the transport of scintillation photons through scintillator and lightguide. The simulation results of plastic scintillator with/without light guides of different surface coverings have been successfully verified with experiments
A semi-analytical study on helical springs made of shape memory polymer
, Article Smart Materials and Structures ; Volume 21, Issue 4 , 2012 ; 09641726 (ISSN) ; Naghdabadi, R ; Arghavani, J ; Sharif University of Technology
2012
Abstract
In this paper, the responses of shape memory polymer (SMP) helical springs under axial force are studied both analytically and numerically. In the analytical solution, we first derive the response of a cylindrical tube under torsional loadings. This solution can be used for helical springs in which both the curvature and pitch effects are negligible. This is the case for helical springs with large ratios of the mean coil radius to the cross sectional radius (spring index) and also small pitch angles. Making use of this solution simplifies the analysis of the helical springs to that of the torsion of a straight bar with circular cross section. The 3D phenomenological constitutive model...
Free-edge stress analysis of general composite laminates under extension, torsion and bending
, Article Applied Mathematical Modelling ; Volume 36, Issue 4 , 2012 , Pages 1570-1588 ; 0307904X (ISSN) ; Sarvestani, M. Y ; Sharif University of Technology
2012
Abstract
In this study, based on the reduced form of elasticity displacement field for a long laminate, an analytical method is established to exactly obtain the interlaminar stresses near the free edges of generally laminated composite plates subjects to extension, torsion, and bending. The constant parameters being in the displacement field, which describe the global deformation of a laminate, are appropriately calculated by using the improved first-order shear deformation theory. Reddy's layerwise theory is subsequently employed for analytical and numerical examinations of the boundary layer stresses within arbitrary laminated composite plates. Various numerical results are developed for the...
Effect of selected parameters on the depositional behaviour of turbidity currents
, Article Journal of Hydraulic Research ; Volume 50, Issue 1 , Dec , 2012 , Pages 60-69 ; 00221686 (ISSN) ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
2012
Abstract
Turbidity currents containing kaolin particles were studied experimentally in a channel and the velocity and concentration profiles were measured using an acoustic Doppler velocimeter. These experiments were performed to investigate the depositional behaviour of turbidity currents. The suspended sediment flux was evaluated by experimental and analytical methods and the results of these two methods were in a good agreement. To evaluate the suspended sediment flux, it was necessary to recognize the suspended sediment zone from the upper shear layer region and near the bed depositional area as well. The method of determination of these areas is discussed. The effects of important parameters...
Static behavior of nano/micromirrors under the effect of Casimir force, an analytical approach
, Article Journal of Mechanical Science and Technology ; Volume 26, Issue 2 , FEB , 2012 , Pages 537-543 ; 1738494X (ISSN) ; Darvishian, A ; Ahmaidan, M. T ; Sharif University of Technology
2012
Abstract
In this paper, static behavior of nano/microm1irrors under Casimir force is studied. At the first, the equilibrium equation governing the statical behavior of nano/micromirrors is obtained. Then energy method is employed to investigate statical stability of nano/micromirrors equilibrium points and a useful equation is suggested for successful and stable design of nano/micromirrors under Casimir force. Then, equilibrium angle of nano/micromirrors is calculated both numerically and analytically using the homotopy perturbation method (HPM). It is observed that with increasing the instability number defined in the paper, the rotation angle of the mirror is increased and suddenly, pull-in occurs....
High temperature synthesis of SAPO-34: applying an L9 taguchi orthogonal design to investigate the effects of experimental parameters
, Article Powder Technology ; Volume 217 , February , 2012 , Pages 223-230 ; 00325910 (ISSN) ; Kazemian, H ; Soltanieh, M ; Hosseinpour, M ; Rohani, S ; Sharif University of Technology
Abstract
SAPO-34 zeolite-like particles were successfully synthesized at high temperature environment. An L9 orthogonal array of the Taguchi method was implemented to investigate the effects of experimental conditions to prepare SAPO-34 with respect to crystallinity of the final product phase. The results showed that the favorable phase crystallinity was improved by increasing the hydrothermal synthesis temperature and organic template content, whereas increasing the water content in synthesis mixture decreased the crystallinity. No significant changes in crystallinity of the final products were observed by increasing the synthesis duration. In addition, zeolite SAPO-5, which was formed as the...
Multi-dimensional correlation steganalysis
, Article MMSP 2011 - IEEE International Workshop on Multimedia Signal Processing ; 2011 ; 9781457714337 (ISBN) ; Diyanat, A ; Ghaemmaghami, S ; Aref, M. R ; Sharif University of Technology
2011
Abstract
Multi-dimensional spatial analysis of image pixels have not been much investigated for the steganalysis of the LSB Steganographic methods. Pixel distribution based steganalysis methods could be thwarted by intelligently compensating statistical characteristics of image pixels, as reported in several papers. Simple LSB replacement methods have been improved by introducing smarter LSB embedding approaches, e.g. LSB matching and LSB+ methods, but they are basically the same in the sense of the LSB alteration. A new analytical method to detect LSB stego images is proposed in this paper. Our approach is based on the relative locations of image pixels that are essentially changed in an LSB...
Design of fractional order proportional-integral-derivative controller based on moment matching and characteristic ratio assignment method
, Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 225, Issue 8 , December , 2011 , Pages 1040-1053 ; 09596518 (ISSN) ; Haeri, M ; Sharif University of Technology
2011
Abstract
This paper presents a new analytical method to design fractional-order proportional- integral-derivative (PID) controllers. The control parameters are calculated so that the closedloop system approximates a desired transfer function with transient response requirements. This function is determined based on the characteristic ratio assignment method. The control parameters are calculated by matching the first three moments of the closed-loop transfer function with the corresponding values of the desired system. Furthermore, to ensure closed-loop stability the proposed method is improved by using the shifted moments around the crossover frequency. Illustrative examples are given to show the...