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Seismic performance of reduced web section moment connections
, Article International Journal of Steel Structures ; Volume 17, Issue 2 , 2017 , Pages 413-425 ; 15982351 (ISSN) ; Kazemi, M. T ; Hoseinzade Asl, M ; Sharif University of Technology
Korean Society of Steel Construction
2017
Abstract
Seismic behavior of beam-to-column connections can be improved by shifting the location of inelasticity away from the column’s face. Such connections can be achieved by reducing the flange area at a specific distance from the beam-column connection, called reduced beam section (RBS), or by reducing web area by introducing a perforation into the web, called reduced web section (RWS). This paper presents a parametric study that is carried out on the effect of the perforation size, perforation location, and the beam span length in the RWS connections, using finite element modeling. Next, an interaction formula is derived for design purposes, and a step by step design method is developed....
Geometrically modified einzel lenses, from the conventional cylindrical einzel lens to cubic and continuous einzel lens
, Article IEEE Transactions on Plasma Science ; Volume 45, Issue 5 , 2017 , Pages 828-835 ; 00933813 (ISSN) ; Yasrebi, N ; Monjezi, H ; Rashidian, B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
New geometrical counterparts to the conventional Einzel lens, cubic, and the continuous body electrostatic (CBE) lenses are introduced and their performances are investigated in terms of different aberrations and input beam properties. Design curves for the continuous body electrostatic lens are presented. Relative sensitivity is proposed as a figure of merit, based on which the focusing characteristics of the two new lenses are compared with that of a conventional Einzel, and a quadrupole lenses of the same size, as well. Moreover, performance and characteristics of the lenses are compared in terms of their corresponding sensitivities to the applied voltage and the incidence beam...
Thermal analysis of laser hardening for different moving patterns
, Article International Journal of Engineering, Transactions A: Basics ; Volume 22, Issue 2 , 2009 , Pages 169-180 ; 17281431 (ISSN) ; Sistaninia, M ; Sharif University of Technology
Materials and Energy Research Center
2009
Abstract
Transient thermal field in laser surface hardening treatment of medium carbon steel was analyzed by employing both three-dimensional analytical model and finite element model. In finite element model the laser beam was considered as a moving plane heat flux to establish the temperature rise distribution in the work-piece, while in analytical model laser beam was considered as an internal heat source. The numerical results were compared with the analytical results. In laser heat treatment of steel some methods are used to produce a wider and nearly uniform average irradiance profile. It may be achieved by rotating the beam optically, thereby producing an overlapping spiral track, or by...
Analysis of micropolar elastic beams
, Article European Journal of Mechanics, A/Solids ; Volume 28, Issue 2 , 2009 , Pages 202-208 ; 09977538 (ISSN) ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
2009
Abstract
In this paper, a linear theory for the analysis of beams based on the micropolar continuum mechanics is developed. Power series expansions for the axial displacement and micro-rotation fields are assumed. The governing equations are derived by integrating the momentum and moment of momentum equations in the micropolar continuum theory. Body couples and couple stresses can be supported in this theory. After some simplifications, this theory can be reduced to the well-known Timoshenko and Euler-Bernoulli beam theories. The nature of flexural and longitudinal waves in the infinite length micropolar beam has been investigated. This theory predicts the existence of micro-rotational waves which...
Reduced active impedance variation by using time modulated array
, Article 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019, 7 July 2019 through 12 July 2019 ; 2019 , Pages 1765-1766 ; 9781728106922 (ISBN) ; Fakharzadeh, M ; Akbari, M ; Safavi Naeini, S ; IEEE Antennas and Propagation Society (APS); The Institute of Electrical and Electronics Engineers (IEEE) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper we investigate the active impedance of Time Modulated Array (TMA) as a low-cost and simple beamforming architecture. Since the antenna elements in TMA are periodically turned on and off, the active impedance of this structure has less variation compared to a phased array architecture. In this paper, we have compared the active impedance of a TMA structure and that of the phased array for different cases. The active reflection coefficient of the TMA is always below-10 dB, while the impedance of the phased array becomes unmatched for certain scan angles
A fast and accurate gate model for small field scattering proton beam therapy
, Article 15th IEEE International Symposium on Medical Measurements and Applications, MeMeA 2020, 1 June 2020 through 3 June 2020 ; 2020 ; Vosoughi, N ; Mahani, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
Proton beam therapy (PBT) is a modern external beam radiation therapy characterized by superior dose distribution. Small field PBT refers to the treatment of tumor sizes less than 7 cm in diameter. In this study, a fast and accurate GATE model was developed and then validated for a small field scattering PBT delivery. To this aim, a fixed single scattering nozzle was modeled in the GATE platform. To accelerate the GATE simulations, a variance reduction technique (VRT) was also incorporated by ignoring the tracking of the secondary particles having a range below a predefined cutoff. In addition, the influence of collimator material on the model performance was evaluated. Beam uniformity,...
Dosimetric evaluation of a newly developed radiochromic film for radiation processing
, Article Iranian Journal of Science and Technology, Transaction A: Science ; Volume 31, Issue 4 , 2007 , Pages 397-401 ; 10286276 (ISSN) ; Sohrabpour, M ; Sharifzadeh, M ; Sharif University of Technology
Shiraz University
2007
Abstract
In order to improve the performance of a newly developed radiochromic film, GIC-79, some dosimetric characteristics of this film have been studied based on relevant standard practice. The present study describes some parameters that may affect the dosimeter response before, during, and after irradiation. The effect of absorbed dose rate on dosimeter response was determined by irradiating dosimeters at low absorbed dose rates with gamma rays. Calibration irradiations of dosimeters were performed with both gamma rays and also electrons to determine the effect of large difference absorbed dose rates on dosimeter response. In addition, post irradiation stability was obtained and also the...
An investigation on the improvement of neutron radiography system of the tehran research reactor by using MCNPX simulations
, Article Nuclear Engineering and Technology ; Volume 53, Issue 10 , 2021 , Pages 3413-3420 ; 17385733 (ISSN) ; Zamzamian, M ; Fadaei, A. H ; Gharib, M ; Feghhi, A. H ; Sharif University of Technology
Korean Nuclear Society
2021
Abstract
Applying the available neutron flux for medical and industrial purposes is the most important application of research reactors. The neutron radiography system is used for non-destructive testing (NDT) of materials so that it is one of the main applications of nuclear research reactors. One of these research reactors is the 5 MW pool-type light water research reactor of Tehran (TRR). This work aims to investigate on materials and location of the beam tube (BT) of the TRR radiography system to improve the index parameters of BT. Our results showed that a through-type BT with 20 cm thick carbon neutron filter, 1.2 cm and 9.4 cm of the diameter of inlet (D1) and output (D2) BT, respectively...
Dispersion and gain investigation of a Cerenkov grating amplifier
, Article IEEE Transactions on Electron Devices ; Volume 50, Issue 6 , 2003 , Pages 1562-1565 ; 00189383 (ISSN) ; Rashidian, B ; Sharif University of Technology
2003
Abstract
The sheet electron beam propagation over a rectangular deep groove grating is investigated and the interaction between surface harmonic waves, which are evanescent above the grating surface, with a dilute sheet electron beam is analyzed. It is assumed that a strong axial magnetic field is applied to constrain the motion of electrons along the waveguide axis. Under these conditions, a complex dispersion equation is derived and analyzed by using Taylor expansion. This expansion results in an analytical formulation for the gain. Using the derived analytical formulation of the gain, the effects of beam thickness, beam-grating gap, and characteristics of grating on gain is investigated
A novel concept for a deformable joint in offshore structures
, Article Proceedings of the 21st International Conference on Offshore Mechanics and Arctic Engineering (OMAE), Oslo, 23 June 2002 through 28 June 2002 ; Volume 1 , 2002 , Pages 503-511 ; England, G. L ; Mahboub-Farimani, M. R ; ASME ; Sharif University of Technology
2002
Abstract
A new semi-rigid beam-to-column, as well as bracing-to-frame, connection has been developed. In addition to its application in building structures, due to its special features and characteristics, it can best lend itself to offshore jackets, where fracture caused by fatigue has always been a major concern. The adverse effects of welding, material embrittlement, residual stresses, etc., pronounced by cyclic loading on such structures, can be overcome by using this new connection. Moreover, it can be easily used in the structure of various modules used in the topside of platforms and FPSOs. The particular feature of this connection is its geometry, which is so devised that it allows much...
Simulation of Wave Propagation in the Sea
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor)
Abstract
In positioning and navigation, Sonar with utilization of sound waves in water environments is similar to the role of Radar in not watered (irrigated) environments. In the Sonar field, modeling and simulation of propagation of sound waves in the undersea environment is a fundamental and very important topic. Nowadays simulation is significant tool that allow to the researchers to predict the quality of Sonar function respect to the experimental conditions. For simulation and modeling of sound wave propagation are used two different methods; Wave theory and Ray theory. In the wave theory, because of the large volume of data, the interpretation of the results is hard. Also in this method cannot...
An Analytical Approach to Nonlinear Vibrations of a Three-Layered Sandwich Beam with a Viscoelastic Core, under the Effects of Internal Resonance, Employing MMS
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor)
Abstract
Vibrations with high amplitudes in continuous systems and models with multiple degrees of freedom, in specific conditions, is concomitant with a phenomenon called internal resonance. In the presence of this phenomenon, energy is transferred from one directly excited mode to the other vibrating modes of the structure results in response of the structure to be combination of the excited modes. In that situation occurrence of the internal resonance may decrease the level of undesired vibrations of the structure. This behavior is of interest especially in sandwich structures with viscoelastic cores that are designated to improve the damping characteristics of the structure and the property may...
Nonlinear Vibration Analysis of a Closed Ends ,Fluid-Filled Beam with Different Boundary Condition, Using Galerkin Method
, M.Sc. Thesis Sharif University of Technology ; Dehghani Firoozabadi, Rouhollah (Supervisor)
Abstract
Presence of fluid in closed ends beam can increase beam hardness against pressure and buckling loads. This behavior is due to incompressibility or very low compressibility of fluids. there is a lot of research in the literature focusing on fluid solid interaction in pipe flow, but there is not any reported research studying on fluid filled beam, where fluid doesn’t flow across the beam. In this research hollow beam is modeled with Euler -Bernoulli beam theorem. Potential energy and kinetic energy is derived with considering the incompressibility of fluid. Nonlinear system of equations is derived using Hamilton principle . this system is taken to time domain using Galerkin and assumed mode...
Design and operation of a simple beam shaping system
, Article Journal of Applied Sciences ; Volume 9, Issue 18 , 2009 , Pages 3350-3356 ; 18125654 (ISSN) ; Golnabi, H ; Shakouri, M ; Sharif University of Technology
2009
Abstract
Design and performance of a beam shaping device based on a simple flexible plastic fiber-bundle stripe and a prism duct is described in this study. Such a system offers practical means to modify and change the output beam shape and also provides quantitative information concerning the transmitted power. It is possible to measure transmitted power signal by using a precise photodetector and also analyze beam images taken by a digital camera. The photograph picture of the illuminating LED beam just at its output point shows a circular shape with a radius of about 4 mm and the fiber-bundle output beam is rectangular shape with a dimension of 22.5×2 mm. A regular duct is tested in this study and...
A new continuous model for flexural vibration analysis of a cracked beam
, Article Polish Maritime Research ; Volume 15, Issue 2 , July , 2008 , Pages 32-39 ; 12332585 (ISSN) ; Ebrahimi, A ; Meghdari, A ; Sharif University of Technology
2008
Abstract
In this paper a new continuous model for vibration analysis of a beam with an open edge crack is presented. A quasi-linear displacement filed is suggested for the beam and the strain and stress fields are calculated. The equation of motion of the beam is calculated using the Hamilton principle. The calculated equation of motion is solved with a modified weighted residual method and the natural frequencies and mode shapes are obtained. The results are compared with those obtained by finite element method and an excellent agreement has been observed. The presented model is a simple and accurate method for analysis of the cracked beam behavior near or far from the crack tip
Free vibration analysis of cross-ply layered composite beams with finite length on elastic foundation
, Article International Journal of Computational Methods ; Volume 5, Issue 1 , 2008 , Pages 21-36 ; 02198762 (ISSN) ; Kargarnovin, M. H ; Ahmadian, M. T ; Sharif University of Technology
2008
Abstract
In this paper, free vibration analysis of cross-ply layered composite beams (LCB) with finite length and rectangular cross-section rested on an elastic foundation is investigated by finite element method. Based on the Timoshenko beam theory which includes the shear deformation and rotary inertia, the stiffness and mass matrices of a LCB are obtained using the energy method. Then, the natural frequencies are calculated by employing eigenvalue technique. The obtained results are verified against existing data in the literatures for a LCB with no foundation and uniform cross-section. Good agreements are observed between these cases. In the same way, the natural frequencies of a specific case,...
Dynamic behavior and modal control of beams under moving mass
, Article Journal of Sound and Vibration ; Volume 306, Issue 3-5 , 2007 , Pages 712-724 ; 0022460X (ISSN) ; Rahimzadeh Rofooei, F ; Shadnam, M. R ; Sharif University of Technology
Academic Press
2007
Abstract
The constitutive equation of an Euler-Bernoulli beam under the excitation of moving mass is considered. The dynamics of the uncontrolled system is governed by a linear, self-adjoint partial differential equation. A Dirac-delta function is used to describe the position of the moving mass along the beam and its inertial effects. An approximate formulation to the problem is obtained by limiting the inertial effect of the moving mass merely to the vertical component of acceleration. Having defined a "critical velocity" in terms of the fundamental period and span of the beam, it is shown that for smaller velocities, the approximate and exact approaches to the problem almost coincide. Since, the...
Flexural-torsional behavior of thin-walled composite beams with closed cross-section
, Article Thin-Walled Structures ; Volume 45, Issue 7-8 , 2007 , Pages 699-705 ; 02638231 (ISSN) ; Haddadpour, H ; Kouchakzadeh, M. A ; Sharif University of Technology
2007
Abstract
This paper investigates the static and dynamic characteristics of composite thin-walled beams that are constructed from a single-cell box. The structural model considered herein incorporates a number of nonclassical effects, such as material anisotropy, transverse shear, warping inhibition, nonuniform torsional model and rotary inertia. The governing equations were derived using extended Hamilton's principle and solved using extended Galerkin's method. The effects of fiber orientation on static deflection and natural frequencies are considered and a number of important conclusions are outlined. © 2007 Elsevier Ltd. All rights reserved
A continuous model for forced vibration analysis of a cracked beam
, Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005, Orlando, FL, 5 November 2005 through 11 November 2005 ; Volume 74 DSC, Issue 2 PART B , 2005 , Pages 1849-1855 ; 0791842169 (ISBN); 9780791842164 (ISBN) ; Meghdari, A ; Ebrahimi, A ; Sharif University of Technology
2005
Abstract
In this paper the equation of motion and corresponding boundary conditions has been developed for forced bending vibration analysis of a beam with an open edge crack. A uniform Euler-Bernoulli beam and the Hamilton principle have been used in this research. The natural frequencies and the forced response of this beam have been obtained using the new developed model in conjunction with the Galerkin projection method. The crack has been modeled as a continuous disturbance function in displacement filed which could be obtained from fracture mechanics. The results show that the first natural frequency will reduce when the crack depth ratio increases. Also the rate of this reduction depends on...
Flat-top beam profile generated using a fiber-bundle prism-coupled beam shaper
, Article Optics Communications ; Volume 284, Issue 12 , June , 2011 , Pages 2817-2824 ; 00304018 (ISSN) ; Golnabi, H ; Sharif University of Technology
2011
Abstract
In this paper, an optical beam shaping system is theoretically and experimentally investigated. The optical system design software ZEMAX is used to simulate and analyze the reported beam shaping design. By using this software ray tracing diagrams are presented with the aim of studying the direct beam propagation, total reflection rays, and the lost rays. The prism duct output beam shape and radiance profiles in both position space and angle space are also studied. For experimental investigation, a two-stage beam shaping design including a fiber-bundle and a prism duct is used. A source light is used for the fiber-bundle illumination and the photograph image of the output beam is taken by a...