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Closed-form solution of natural frequencies of a cantilever beam under longitudinal rotation of the support
, Article DETC2005: ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Long Beach, CA, 24 September 2005 through 28 September 2005 ; Volume 1 A , 2005 , Pages 145-151 ; 0791847381 (ISBN); 9780791847381 (ISBN) ; Durali, M ; Jalili, N ; Sharif University of Technology
American Society of Mechanical Engineers
2005
Abstract
This paper presents the modeling steps towards development of frequency equations for a cantilever beam with a tip mass under general base excitations. More specifically, the beam is considered to vibrate in all the three directions, while subjected to a base rotational motion around its longitudinal direction. This is a common configuration utilized in many vibrating beam gyroscopes and well drilling systems. The governing equations are derived using Extended Hamilton's Principle with general 6-DOF base motion. The natural frequency equations are then extracted in closed-form for the case where the base undergoes longitudinal rotation. For validation purposes, the resulting natural...
Prediction of the Contribution of Mass Transfer During Jet Formation in Liquid-Liquid Extraction Columns
, M.Sc. Thesis Sharif University of Technology ; Sayf Kordi, Ali Akbar (Supervisor)
Abstract
There are many different opinions about the mass transfer contribution during jet formation in liquid - liquid extraction columns, and this could impact on their design. In this work, using experimental data obtained in two RDC columns and unpublished data of the jet mass transfer coefficients, mass transfer can be predicted during jet formation. The jet length and diameter were anticipated by using existing relations, and then the jet mass transfer coefficient was predicted, jet mass transfer rate and total column mass transfer rate were calculated and finally the contribution of mass transfer during jet formation in the column was predicted. Mass transfer contribution in the jet in various...
Measuring of the Barrier around of the C-N Band in the Molecule of 2-Cyano Ethyl Morpholine-4-Carbo Dithioate by DNMR
, M.Sc. Thesis Sharif University of Technology ; Tafazzoli, Mohsen (Supervisor)
Abstract
In this research, the barrier around C-N bond in the molecule of 2-cyano ethyl morpholine-4-carbo dithioate was calculated by dynamic NMR. The 1H-NMR spectra of sample were recorded between temperatures of 240-332 K and 240-328 K in chloroform and acetone solvents, respectively. By analyzing the spectra by SpinWorks software, thermodynamic parameters (ΔG# , ΔH# , ΔS# ) extracded and compared with the data of quantum calculations . In quantum calculations, we compared data in two level (HF and B3LYP ).Consequently, the data of B3LYP method was better .Experimental ΔG# for internal rotation around C-N bond in 2-cyano ethyl morpholine-4-carbo dithioate was 14.04 kcal mol -1 and compared to...
A robust and invariant keypoint extraction algorithm in brain MR images
, Article Communications in Computer and Information Science ; Vol. 427, issue , Sep , 2014 , p. 121-130 ; 9783319108483 ; Abdollahian, E ; Shirpour, M ; Javaheri, A ; Manzuri, M.T ; Sharif University of Technology
Abstract
In this paper a method for extracting keypoints from human brain MR images is proposed. These keypoints are obtained based on curved structures in the brain MR images. In this method, a keypoint is center of a circle which includes circular boundaries in the image and is selected based on gradients of the image. These keypoints and their descriptors are scale and rotation invariant. The proposed method is compared with other well-known methods with repeatability measure and ROC curves. Experimental results show that proposed method performs better than other well-known methods, specially, when deformations are remarkable
Theory of the liquid film motor
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 3 , September , 2015 ; 15393755 (ISSN) ; Namin, R. M ; Amjadi, A ; Sharif University of Technology
American Physical Society
2015
Abstract
The liquid film motor is a freely suspended liquid film placed between two capacitively coupled plates that rotates when an electric current is passed through it. Here we propose a theory for its rotation mechanism based on thin film electroconvection. The capacitively coupled plates induce free charges on the surfaces of the film, and the electric field on the film exerts a force that induces rotation. Results of the proposed theory and simulation are in good agreement with the experiments in different properties of the liquid film motor
Empirical assessment of the performance characteristics in turbocharger turbine and compressor
, Article Experimental Techniques ; Volume 34, Issue 3 , July , 2010 , Pages 54-67 ; 07328818 (ISSN) ; Rad, M ; Shahhosseini, M. R ; Sharif University of Technology
2010
Abstract
The performance parameter uncertainties of turbomachines at different rotational speed were determined by experimental and analytical consideration. The instruments/sensors were located and installed according to the standards for evaluating the performance characteristics of turbine and compressor in a turbocharger laboratory in a wide range of rotational speeds. The comparison of turbine and compressor sensitivity shows that the sensitivity of compressor to 1% shift in the pressure is higher than that for the turbine. Results also show that the sensitivities of efficiency and power of turbine reduce as rotational speed increases. The total uncertainty of turbine and compressor are obtained...
Numerical and experimental investigation of the vibration of rotors with loose discs
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 224, Issue 1 , 2010 , Pages 85-94 ; 09544062 (ISSN) ; Asayesh, M ; Sharif University of Technology
2010
Abstract
In this study, the energy method has been used to develop a finite-element code for studying the effects of loose rotating discs on the rotor-bearing systems' response. A mathematical model of the loose disc has resulted in terms similar to unbalance and gyroscopic effects in the equation of motion of the system. Results of this study show that rotor response and beating phenomena are a function of measurement location, loose disc mass and inertia, ratio of rotating speed to the speed of loose disc, and clearance between the loose disc and shaft considering constant speed for loose disc and shaft. The developed finite-element model can numerically give the response of rotors with any number...
Stellar rotation effects in polarimetric microlensing
, Article Astrophysical Journal ; Volume 825, Issue 2 , 2016 ; 0004637X (ISSN) ; Sharif University of Technology
Institute of Physics Publishing
2016
Abstract
It is well known that the polarization signal in microlensing events of hot stars is larger than that of main-sequence stars. Most hot stars rotate rapidly around their stellar axes. The stellar rotation creates ellipticity and gravity-darkening effects that break the spherical symmetry of the source's shape and the circular symmetry of the source's surface brightness respectively. Hence, it causes a net polarization signal for the source star. This polarization signal should be considered in polarimetric microlensing of fast rotating stars. For moderately rotating stars, lensing can magnify or even characterize small polarization signals due to the stellar rotation through polarimetric...
Vibration analysis of a rotating nanoplate using nonlocal elasticity theory
, Article Journal of Solid Mechanics ; Volume 9, Issue 2 , 2017 , Pages 319-337 ; 20083505 (ISSN) ; Shafiei, N ; Alavi, S. H ; Sharif University of Technology
Islamic Azad University
2017
Abstract
The nanostructures under rotation have high promising future to be used in nanomachines, nano-motors and nano-turbines. They are also one of the topics of interests and it is new in designing of rotating nano-systems. In this paper, the scaledependent vibration analysis of a nanoplate with consideration of the axial force due to the rotation has been investigated. The governing equation and boundary conditions are derived using the Hamilton's principle based on nonlocal elasticity theory. The boundary conditions of the nanoplate are considered as free-free in y direction and two clamped-free (cantilever plate) and clamped-simply (propped cantilever) in x direction. The equations have been...
Thermal performance of rotating closed-loop pulsating heat pipes: experimental investigation and semi-empirical correlation
, Article International Journal of Thermal Sciences ; Volume 123 , 2018 , Pages 14-26 ; 12900729 (ISSN) ; Alhuyi Nazari, M ; Behshad Shafii, M ; Sharif University of Technology
Elsevier Masson SAS
2018
Abstract
A rotating closed loop pulsating heat pipe (RCLPHP) was experimentally investigated as a passive heat sink for rotary equipment cooling. The effects of heat input, rotational speed, filling ratio, and working fluid on the thermal resistance of RCLPHP were studied. Pure water and ethanol were used as working fluids with filling ratios of 30%, 50%, and 70% by volume, and the RCLPHP was tested at four rotational speeds: 200, 400, 600, and 800 rpm. The results showed that the best filling ratio for both water and ethanol is 50% and proved that the RCLPHP is able to work efficiently in a wide range of rotational speed. Moreover, it was observed that at the optimum filling ratio for ethanol and...
Free vibration analysis of rotating laminated cylindrical shells under different boundary conditions using a combination of the layerwise theory and wave propagation approach
, Article Scientia Iranica ; Volume 16, Issue 2 B , 2009 , Pages 168-176 ; 10263098 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
2009
Abstract
In this paper, vibration analysis of rotating laminated composite cylindrical shells using a combination of the layerwise theory and wave propagation approach is investigated. This combination enables us to study all the conventional boundary conditions in our analysis. Results obtained have been compared with those available in the literature and a good agreement has been observed. In contrast to the Equivalent Single Layer theories (ESL), the layerwise theory is constructed on the basis ofC°- continuity through the laminate thickness. For the surface of the shell, a displacement field based on the wave propagation approach is proposed. The effect of Coriolis and centrifugal accelerations...
Enhancing the roll dynamics of an AUV by contra-rotating-propellers
, Article Ships and Offshore Structures ; 2020 ; Kamali, A ; Abbaspour, M ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
Roll control of the Autonomous Underwater Vehicles (AUVs) is a significant issue in the current field of research for many researchers in the subject of AUV control system designation. Especially at higher speeds, the roll angle generated by a single rotating propeller or other external disturbances can considerably influence the whole dynamics and therefore the operation of the vehicle. In this paper, the utilisation of a system of contra-rotating-propellers (CRP) to enhance the roll dynamics of an AUV is evaluated by developing a six-degrees-of-freedom (6DOF) dynamics and control systems’ simulator. The results show that: 1. The single propeller system can cause roll angle deflections...
On normal subgroups of the unit group of a quaternion algebra over a pythagorean field
, Article Bulletin of the Iranian Mathematical Society ; Volume 46, Issue 1 , June , 2020 , Pages 253-262 ; Sharif University of Technology
Springer
2020
Abstract
We investigate the structure of normal subgroups of the unit group of a quaternion algebra over a pythagorean field. © 2019, Iranian Mathematical Society
Study of the effect of fluid flow on corrosion rate for simple carbon steel in aqueous solution using rotating disk electrode
, Article 18th International Congress of Chemical and Process Engineering, CHISA 2008, Prague, 24 August 2008 through 28 August 2008 ; 2008 ; Mohagheghi, A ; Sharif University of Technology
2008
Abstract
The influence of fluid flow on the corrosion of simple carbon steel ST37 (AISI 1020) in aqueous solution of Bandar-Abbas gas well was studied at 25°C under air-saturated condition. The mechanism and kinetic of corrosion in different hydrodynamic conditions were determined using a rotating disk electrode. Increasing the velocity of rotating disk ≤ 1000 rpm caused an augmentation in corrosion rate from 9.89 to 18.95 mill in./yr. Increasing the velocity beyond 1000 rpm changed the corrosion mechanism so that the activation polarization will control the corrosion process, and the variation in corrosion rates was due to various corrosion mechanisms rather than mass transfer of reactant component....
An analytical and experimental investigation on the normal grain growth in metals using the Monte Carlo method
, Article Materials and Design ; Volume 28, Issue 9 , 2007 , Pages 2533-2539 ; 02613069 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
Elsevier Ltd
2007
Abstract
The prediction of material microstructure is of great interest to the material designers since the property and performance of materials depend strongly on their microstructures. In this work, a Monte Carlo approach is used to investigate the normal grain growth of aluminum and pure copper. The grain growth was calculated at certain temperatures using the grain growth law and compared with the simulation results by varying the Q as a parameter of simulation lattice orientation for pure aluminum. Also the results predicted by the Monte Carlo method showed a good agreement with the experimental results of grain growth of pure cooper. It was found that increase in Q increases the accuracy of...
On rotational ambiguity in model-free analyses of multivariate data
, Article Journal of Chemometrics ; Volume 20, Issue 6-7 , 2006 , Pages 302-310 ; 08869383 (ISSN) ; Mason, C ; Tauler, R ; Jalali Heravi, M ; Maeder, M ; Sharif University of Technology
2006
Abstract
Rotational ambiguity is a central but not well investigated problem in all soft-modelling analyses of multivariate data. A novel method which is based on Resolving Factor Analysis (RFA) is proposed. Completely general and exhaustive results are presented for the two-component case. In particular the effects of noise and global analysis of series of measurements are investigated. Copyright © 2007 John Wiley & Sons, Ltd
Encoding the information in relative parameters
, Article Physics Letters, Section A: General, Atomic and Solid State Physics ; Volume 407 , 2021 ; 03759601 (ISSN) ; Mani, A ; Sharif University of Technology
Elsevier B.V
2021
Abstract
We investigate the problem of communicating three parameters in the absence of shared reference frame. We explore two methods in which the relative angles of spins are used to encode the parameters. In the first method we use three spins that carry the information in their relative angles while in the second method we use three disjoint spin-pairs and the information is sent through the relative angles of each individual pair. We show that in the first method, the information conveyed by each qubit is more than the second one, and that is while it requires fewer particles. © 2021 Elsevier B.V
Optimization of parameters for the friction stir processing and welding of aa1050 aluminum alloy
, Article Iranian Journal of Materials Science and Engineering ; Volume 18, Issue 2 , 2021 ; 17350808 (ISSN) ; Ebadi, M ; Kokabi, A. H ; Sharif University of Technology
Iran University of Science and Technology
2021
Abstract
Friction-Stir Processing (FSP) was applied on AA1050 Aluminum Alloy (AA) to find the highest mechanical properties among 28 combinations of the rotational and traverse speed (800-2000 rpm and 50-200 mm.min-1) and four different tool probe shapes (threaded, columnar, square and triangle). To this aim, the AA standard sheet went through a single pass of FSP. The 1600 rpm and 100 mm.min-1 with threaded tool probe was chosen as the best combination of rotational and traverse speed. Grain size at the Stirred Zone (SZ) was studied using Optical Microscopy (OM). The results showed that the SZ’s grain size was refined from 30 μm down to about 12 μm due to dynamic recrystallization during FSP. The...
Spatial rational motions based on Rational Frenet-Serret curves
, Article 2004 IEEE International Conference on Systems, Man and Cybernetics, SMC 2004, The Hague, 10 October 2004 through 13 October 2004 ; Volume 5 , 2004 , Pages 4456-4461 ; 1062922X (ISSN) ; 0780385667 (ISBN) ; Meghdari, A ; Sharif University of Technology
2004
Abstract
The aim of this paper is to demonstrate that the techniques of Computer Aided Geometric Design such as spatial rational curves and surfaces could be applied to Kinematics, Computer Animation and Robotics. For this purpose we represent a method which utilizes a special class of rational curves called Rational Frenet-Serret (RF) curves for spatial rational motion design. RF curves distinguished by the property that the motion of their Frenet-Serret frame is rational. We describe an algorithm for interpolation of positions by a rational Frenet-Serret motion. Further more we provide an analysis on spatial frames (Frenet-Serret frame and Rotation Minimizing frame). Also we derive and algorithm...
Effect of centrifugal force on natural frequency of lateral vibration of rotating shafts
, Article Journal of Sound and Vibration ; Volume 274, Issue 3-5 , 2004 , Pages 985-995 ; 0022460X (ISSN) ; Bastami, A. R ; Sharif University of Technology
Academic Press
2004
Abstract
This paper investigates the effect of shaft rotation on its natural frequency. Apart from gyroscopic effect, the axial force originated from centrifugal force and the Poisson effect results in change of shaft natural frequency. D'Alembert principle for shaft in cylindrical co-ordinate system, along with the stress-strain relation, gives the non-homogenous linear differential equation, which can be used to calculate axial stress in the shaft. Numerical results of this study show that axial stress produced by shaft rotation has a major effect on the natural frequency of long high-speed shafts, while shaft diameter has no influence on the results. In addition, change in lateral natural...