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Applying Contour Integral method for analysis of substrate integrated waveguide filters
, Article 2010 10th Mediterranean Microwave Symposium, MMS 2010, 25 August 2010 through 27 August 2010 ; August , 2010 , Pages 418-421 ; 9781424472437 (ISBN) ; Banai, A ; Sharif University of Technology
2010
Abstract
In this paper the Contour Integral (CI) method is applied to the design and analysis of substrate integrated waveguide (SIW) filters. This method is used for planar structures and is based upon the discretization of the boundary of the structure and needs less memory than full wave methods. For decreasing the computation time, circular vias replaced by square ones. A four pole Chebyshev X band dual inductive post substrate integrated waveguide filter is designed using this technique and the results are compared with measurements and simulation software Ansoft HFSS. Good agreement is seen between the results
Flow of a PTT fluid through planar contractions - Vortex inhibition using rounded corners
, Article ASME 2010 International Mechanical Engineering Congress and Exposition, IMECE 2010, Vancouver, BC, 12 November 2010 through 18 November 2010 ; Volume 7, Issue PARTS A AND B , November , 2010 , Pages 601-607 ; 9780791844441 (ISBN) ; Ramazani S. A, A ; Hosseini Amoli, H ; Behrang, A ; Kamyabi, A ; Sharif University of Technology
2010
Abstract
Contraction flow is one of important geometries in fluid flow both in Newtonian and non-Newtonian fluids. In this study, flow of a viscoelastic fluid through a planar 4:1 contraction with rounded corners was investigated. Six different rounding ratios (RR =0, 0.125, 0.25, 0.375, 0.438, 0.475, 0.488) was examined using the linear PTT constitutive equation at creeping flow and isothermal condition. Then the resulting PDE set including continuity, momentum, and PTT constitutive equations were implemented to the OpenFOAM software. The results clearly show vortex deterioration with increasing rounding diameter, so that when rounding corner exceeds a critical value, the vortex disappears...
The inapproximability for the (0,1)-additive number
, Article Discrete Mathematics and Theoretical Computer Science ; Volume 17, Issue 3 , 2016 , Pages 217-226 ; 14627264 (ISSN) ; Dehghan, A ; Sharif University of Technology
Discrete Mathematics and Theoretical Computer Science
2016
Abstract
An additive labeling of a graph G is a function H: V(G)→ N, such that for every two adjacent vertices v and u of G, Σw∼v l(w) = Σw∼vl(w) (x ∼ y means that x is joined to y). The additive number of G, denoted by η(G), is the minimum number k such that G has a additive labeling l: V(G)→ Nk. The additive choosability of a graph G, denoted by ηl(G), is the smallest number k such that G has an additive labeling for any assignment of lists of size k to the vertices of G, such that the label of each vertex belongs to its own list. Seamone in his PhD thesis conjectured that for every graph G, η(G) = ηe(G). We give a negative answer to this conjecture and we show that for every k there is a graph G...
Synthesis, crystal structures and Hirshfeld surface analyses of two new Salen type nickel/sodium heteronuclear complexes
, Article Journal of Molecular Structure ; Volume 1110 , 2016 , Pages 119-127 ; 00222860 (ISSN) ; Behzad, M ; Tarahhomi, A ; Maroney, M ; Rudbari, H. A ; Bruno, G ; Ghanbari, B ; Sharif University of Technology
Elsevier
Abstract
Two new heteronuclear Nickel(II)/Sodium(I) complexes of a side-off compartmental Schiff base ligand were synthesized and characterized by spectroscopic methods. Crystal structures of both of the complexes were also obtained. The Schiff base ligand was synthesized from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with 2-hydroxy-3-methoxybenzaldehyde. In both of the complexes the Ni(II) ion is coordinated to the inner N2O2 coordination sphere with square-planar geometry and the Na(I) ion is coordinated to the outer O2O2′ coordination sphere. In Complex (1) with general formula [Ni(L)Na(CH3OH)(ClO4)] the sodium ion is seven coordinated while in (2) with general formula...
Continuum modelling of a circular planar array of coupled microwave oscillators
, Article European Microwave Week 2009, EuMW 2009: Science, Progress and Quality at Radiofrequencies, Conference Proceedings - 39th European Microwave Conference, EuMC 2009, 28 September 2009 through 2 October 2009, Rome ; 2009 , Pages 1349-1352 ; 9782874870118 (ISBN) ; Banai, A ; Sharif University of Technology
Abstract
in this paper the phase distribution in an array of coupled oscillators arranged on a circular surface is discussed. Coupling is considered to be weak and each oscillator is coupled to its four nearest neighbours. In a continuum limit where the number of oscillators goes to infinity a theoretical formulation in polar coordinates is proposed to describe the dynamic behaviour of phases of the array elements. A Green's function for phase distribution of the array is proposed in terms of its normalized eigenfunctions. Beam steering can be done via detuning the edge oscillators. © 2009 EuMA
Various coupling configurations on the performance of two-dimensional coupled oscillator arrays
, Article IET Microwaves, Antennas and Propagation ; Volume 11, Issue 3 , 2017 , Pages 426-432 ; 17518725 (ISSN) ; Banai, A ; Sharif University of Technology
Institution of Engineering and Technology
2017
Abstract
Coupled oscillator arrays (COAs) can be used to control the phase distribution across the aperture of an array antenna in such a manner as to affect steering of the beam without the use of phase shifters. Given the various possible planar configurations of COAs, a systematic design approach is necessary. In this study, the authors present a comprehensive comparison of various configurations of planar COAs based on their sensitivity to random errors in their free running frequencies. The parameters considered are (a) the beam pointing error of the array, (b) the locking probability, (c) the side lobe level, and (d) the beam width of the radiation pattern. These results can serve as a design...
Blue and red wavelength resolved impedance response of efficient perovskite solar cells
, Article Sustainable Energy and Fuels ; Volume 2, Issue 11 , 2018 , Pages 2407-2411 ; 23984902 (ISSN) ; Tavakoli, M. M ; Turren Cruz, S. H ; Pandey, K ; Saliba, M ; Yadav, P ; Sharif University of Technology
Royal Society of Chemistry
2018
Abstract
The identification of recombination centers in perovskite solar cells is highly challenging. Here, we demonstrate the red and blue excitation wavelength resolved impedance response in state-of-the-art perovskite solar cells (PSCs) providing insights into charge recombination and ion accumulation. To get insight into the interfacial electronic characteristics, we fabricated PSCs with a planar architecture containing state-of-the-art triple-cation perovskite materials as absorber layers. The capacitance-frequency response under various blue and red illumination conditions were used to investigate interfacial charge accumulations and found that under high energy photons irradiation maximum...
Optimum design of planar transformer for LLC resonant converter using metaheuristic method
, Article 45th Annual Conference of the IEEE Industrial Electronics Society, IECON 2019, 14 October 2019 through 17 October 2019 ; Volume 2019-October , 2019 , Pages 6621-6626 ; 9781728148786 (ISBN) ; Tahami, F ; Sharif University of Technology
IEEE Computer Society
2019
Abstract
Isolated, high-density DC-DC converters play a crucial role in the power supply unit of information technology industries. By virtue of high efficiency and high power density, LLC resonant converters-among the rest of DC-DC converters-are suitable candidates for this application. The magnetic structure of this converter, however, is a bulky, dissipative part, which has a considerable portion of power loss. Improvement in the size and efficiency of the LLC transformer will lead to an overall enhancement of power density and efficiency of the converter. Nevertheless, the optimization of planar transformers for the LLC converter has not been studied enough. This paper proposes a...
Low swirl premixed methane-air flame dynamics under acoustic excitations
, Article Physics of Fluids ; Volume 31, Issue 9 , 2019 ; 10706631 (ISSN) ; Farshchi, M ; Chakravarthy, S. R ; Chakraborty, A ; Aravind, I. B ; Wang, B ; Sharif University of Technology
American Institute of Physics Inc
2019
Abstract
In this study, simultaneous particle image velocimetry and planar laser induced fluorescence of hydroxyl radical, chemiluminescence imaging, and hot-wire measurements are utilized to study reacting low swirl flow dynamics under low to high amplitude acoustic excitations. Results show that a temporal weak recirculation zone exists downstream of the flame, which is enlarged in size under acoustic excitations. Investigations show that temporal behaviors of this recirculation zone play a significant role in flame movements and instabilities. As the acoustic wave amplitude increases, the flame lift-off distance changes drastically, resulting in flame instabilities (flashback and blowout) during...
Greatly reduced radiation loss in planar waveguides with two-dimensional conducting interfaces
, Article IET Optoelectronics ; Volume 2, Issue 4 , 2008 , Pages 158-164 ; 17518768 (ISSN) ; Zareian, N ; Mehrany, K ; Sharif University of Technology
2008
Abstract
A new strategy for radiation loss reduction in curved slab waveguides is presented. The proposed strategy is based on the proper modification of the boundary conditions at the core-to-cladding interface, whereupon extremely thin conductive nanolayers with non-zero surface conductance are imposed. The obtained numerical results show a noticeable decrease in the overall loss level. © 2008 The Institution of Engineering and Technology
Quantum nonlinear planar Hall effect in bilayer graphene: An orbital effect of a steady in-plane magnetic field
, Article Physical Review B ; Volume 106, Issue 24 , 2022 ; 24699950 (ISSN) ; Langari, A ; Sharif University of Technology
American Physical Society
2022
Abstract
We study the quantum nonlinear planar Hall effect in bilayer graphene under a steady in-plane magnetic field. When time-reversal symmetry is broken by the magnetic field, a charge current occurs in the second-order response to an external electric field as a result of the Berry curvature dipole in momentum space. We show that a nonlinear planar Hall effect originating from the anomalous velocity is caused by an orbital effect of an in-plane magnetic field on electrons in bilayer graphene in the complete absence of spin-orbit coupling. Taking into account the symmetry analysis, we derive the dominant dependence of the Berry curvature dipole moment on the magnetic field components. Moreover,...
Wideband Microwave Radio Direction Finding Based on Phase Interferometry Method for Two and Three Dimensional Arrays with Minimum Number of Antennas
, Ph.D. Dissertation Sharif University of Technology ; Farzaneh, Forouhar (Supervisor)
Abstract
The interferometer method, as one of the most accurate schemes for wideband direction finding (DF), is used. The interferometer method has various algorithms which can be implemented depending on the required specifications. The advantages and disadvantages of these algorithms have been evaluated and the appropriate algorithm for a general practical case in view of the ambiguity resolution is proposed. The receivers’ channel phase tracking error is of significant concern in practice, in interferometric DF systems. The induced error due to channels phase tracking error is estimated. Furthermore the use of physically realizable antennas, achievement of high accuracy, minimum number of antennas...
Common Mode Noise Reduction of LLC Resonant Converter with Planar Transformer for Electric Vehicle Applications
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
converters in electric vehicles, it is necessary to reduce their dimensions and increase their efficiency. It is expected that in the near future wide band gap semiconductors will be used to achieve these goals. On the other hand, usage of planar transformers is necessary to achieve slim and compact converter designs in electric vehicles. Clearly, planar transformers offer a significant advantage in replacing bulky wired transformers in high frequency LLC resonant converters with WBG transistors. planar transformers also have several other advantages, including low flux leakage, modular structure, and low thermal resistance.However, in planar transformers, due to the proximity and large area...
Analysis and simulation of ring resonator silicon electro-optic modulators based on PN junction in reverse bias
, Article Optical Engineering ; Vol. 53, issue. 12 , 2014 ; ISSN: 00913286 ; Akbari, M ; Sharif University of Technology
Abstract
The theory of silicon optical modulators of ring resonators based on PN diode in reverse bias is primarily discussed. It secondarily provides a full-featured simulator to investigate the behavior of such modulators. Wave equation for ring structure will be solved by using the conformal transformation method and the matrix method as it was used to analyze bent planar optical waveguides. Power coupling between ring and straight waveguides will be calculated by coupled theory of nonparallel waveguides based on experimental results. The time response demonstrates the capability of this device to operate correctly at up to 10 Gbs-1 bitrate, and the frequency spectrum analysis of device shows a >...
Nonlinear circuit model for discontinuity of step in width in superconducting microstrip structures and its impact on nonlinear effects
, Article IEEE Transactions on Applied Superconductivity ; Volume 23, Issue 2 , 2013 ; 10518223 (ISSN) ; Farzaneh, F ; Fardmanesh, M ; Sharif University of Technology
2013
Abstract
Superconducting materials are known to exhibit nonlinear effects and to produce harmonic generation and intermodulation distortion in superconductive circuits. In planar structures, these nonlinearities depend on the current distribution on the strip which is mainly determined by the structure of the device. This paper investigates the current distribution at the step-in-width discontinuity in superconducting microstrip transmission lines, which is computed by a numerical approach based on a 3-D finite-element method. This current distribution is used to obtain the parameters of the nonlinear circuit model for the superconducting microstrip step-in-width discontinuity. The proposed...
Single-Source Capacitated Multi-Facility Weber Problem - An iterative two phase heuristic algorithm
, Article Computers and Operations Research ; Volume 39, Issue 7 , 2012 , Pages 1465-1476 ; 03050548 (ISSN) ; Torabi, S. A ; Eshghi, K ; Sharif University of Technology
2012
Abstract
Multi-Facility Weber Problem (MFWP), also known as continuous locationallocation problem, entails determining the locations of a predefined number of facilities in a planar space and their related customer allocations. In this paper, we focus on a new variant of the problem known as Single-Source Capacitated MFWP (SSCMFWP). To tackle the problem efficiently and effectively, an iterative two-phase heuristic algorithm is put forward. At the phase I, we aim to determine proper locations for facilities, and during the phase II, assignment of customers to these facilities is pursued. As an alternative solution method, a simulated annealing (SA) algorithm is also proposed for carrying out the...
Simulation of flow of short fiber suspensions through a planar contraction
, Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 579-584 ; 10263098 (ISSN) ; Ramazani S. A. A ; Kamyabi, A ; Hosseini Amoli, H ; Sharif University of Technology
2012
Abstract
In this study, the flow of a fiber filled viscoelastic matrix through planar contractions is investigated. It was found that by adding fiber to the matrix vortex, the intensity increases. Fiber orientation along "x" and "y" axes was studied too. It was found that fiber orientation could be used for determining the flow regime through the contraction geometry. The rigidity condition of fibers, which needs the trace of the orientation tensor to be unity everywhere in the domain, is correct except near walls and the reentrant corner, which is slightly less than one. In these regions, the stress magnitude is higher, which results in more numerical errors, and which further leads to some error in...
Radial basis function network for exponential stabilisation of periodic orbits for planar bipedal walking
, Article Electronics Letters ; Volume 47, Issue 12 , 2011 , Pages 692-694 ; 00135194 (ISSN) ; Hamed, K.A ; Gruver, W. A ; Dumont, G. A ; Sharif University of Technology
2011
Abstract
Presented is a novel and analytical approach to design a hybrid controller based on hybrid zero dynamics for exponential stabilisation of a desired periodic orbit for a hybrid model of walking composed of single and double support phases. To achieve this goal, the effect of a double support phase on angular momentum transfer and stabilisation is investigated. Also, the class of control inputs corresponding to an orbit during double support is presented. A smooth feedback law based on a radial basis function network is then proposed for the double support phase such that (i) the desired orbit is exponentially stable and (ii) the control vector minimises the least square control cost
Dynamic analysis of an n-revolute planar serial manipulator and sensitivity analysis based on Sobol's method
, Article International Conference on Robotics and Mechatronics, ICROM 2015, 7 October 2015 through 9 October 2015 ; 2015 , Pages 569-574 ; 9781467372343 (ISBN) ; Mohammadi, M ; Masouleh, M. T ; Sharif University of Technology
2015
Abstract
In this paper, dynamic modeling and dynamic sensitivity analysis of an n-revolute planar serial robot are investigated. First, a dynamic modeling algorithm is proposed which is based on the concept of the so-called Natural Orthogonal Complement. The main goal of this algorithm consists in deriving the corresponding dynamic equations of a planar serial manipulator systematically. As a comparison study, 3-DOF a planar serial manipulator is modeled and the results of the proposed algorithm is compared with other methods, i.e., Newton-Euler, Lagrange-Euler, Adams software and an Open Dynamics Engine, the so-called MatODE. Then, in order to develop a dynamic sensitivity analysis scheme, Sobol's...
Path planning of 3-RRR parallel robot by avoiding mechanical interferences via Artificial Potential Field
, Article International Conference on Robotics and Mechatronics, ICROM 2015, 7 October 2015 through 9 October 2015 ; 2015 , Pages 240-245 ; 9781467372343 (ISBN) ; Porshokouhi, P. N ; Masouleh, M. T ; Novin, R. S ; Sharif University of Technology
2015
Abstract
This paper deals with the collision-free path planning of planar parallel robot by avoiding mechanical interferences and obstacle within the workspace. For this purpose, an Artificial Potential Field approach is developed. As the main contribution of this paper, In order to circumvent the local minima problem of the potential fields, a novel approach is proposed which is a combination of Potential Field approach, Fuzzy Logic and also a novel algorithm consisting of Following Obstacle as well as Virtual Obstacle methods, as a hybrid method. Moreover, the inverse kinematic problem of the 3-RRR parallel robot is analyzed and then the aforementioned hybrid method is applied to this mechanism in...