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A composite rigid body algorithm for modeling and simulation of an underwater vehicle equipped with manipulator arms
, Article 23rd International Conference on Offshore Mechanics and Arctic Engineering, Vancouver, BC, 20 June 2004 through 25 June 2004 ; Volume 3 , 2004 , Pages 839-853 ; Banae, M ; Meghdari, A ; Sharif University of Technology
2004
Abstract
In this paper modeling and simulation of an underwater vehicle equipped with manipulator arms, using Composite Rigid Body (CRB) algorithm will be discussed. Because of increasing need to Unmanned Underwater Vehicles (UUVs) in oil and gas projects in Persian Gulf, for doing operations such as inspection of offshore jackets, subsea pipelines and submarine cables and also pre installation survey and post laid survey of submarine pipelines and cables, design and construction of "SROV" was developed in Sharif University of Technology, and at design stage behavior of underwater vehicles was studied. In this paper, an efficient dynamic simulation algorithm is developed for an UUV equipped with m...
On the analytical model of beam-to-column semi-rigid connections, using plate theory
, Article Thin-Walled Structures ; Volume 39, Issue 4 , 2001 , Pages 307-325 ; 02638231 (ISSN) ; Ghorbani Asl, M ; McCabe, S. L ; Sharif University of Technology
2001
Abstract
An analytical method is presented that can be used to determine the behavior of a particular steel beam-to-column extended end plate connection, in both linear and non-linear regions. This article demonstrates a closed form solution of the equations of deformation, for this type of connection. Besides, a step-by-step analytical procedure for establishment of the linear part of M-θ curve of this form of connection is developed. However, this technique can properly be extended to the non-linear regions, which is not considered in this article. The correctness of the results has been ascertained by a comparison, using non-linear finite element models as well as experimental approach; and very...
Numerical modeling of MDOF structures with sliding supports using rigid-plastic link
, Article Earthquake Engineering and Structural Dynamics ; Volume 30, Issue 1 , 2001 , Pages 27-42 ; 00988847 (ISSN) ; Hamidi, M ; Ahmadi, G ; Sharif University of Technology
2001
Abstract
In this paper, the responses of multi-degree-of-freedom (MDOF) structures on sliding supports subjected to harmonic or random base motions are investigated. Modeling of the friction force under the foundation raft is accomplished by using a fictitious rigid link which has a rigid-perfectly plastic material. This will result in identical equations of motion for the sliding structure, both in the sliding and non-sliding (stick) phases which greatly simplifies the implementation of the method into a numerical algorithm. In this model the phase transition times are determined with high accuracy. This has two advantages: first, it prevents the so-called high-frequency oscillation of the relative...
Discussion of "Rocking vibration of a rigid disk embedded in any depth of a coupled seawater-visco-poro-elastic seabed half-space" by R. He [Soil Dyn. Earthq. Eng. 85(2016), 130-133]
, Article Soil Dynamics and Earthquake Engineering ; 2016 ; 02677261 (ISSN) ; Samea, P ; Eskandari, M ; Sharif University of Technology
Elsevier Ltd
2016
Feasibility analysis of the use of rigid polyurethane foam in modular sandwich panels for rapid assembly structures
, Article International Journal of GEOMATE ; Volume 15, Issue 51 , 2018 , Pages 113-120 ; 21862982 (ISSN) ; Nemati, S ; Sharafi, P ; Yaghmaei, F ; Farrokhi, A ; Sharif University of Technology
GEOMATE International Society
2018
Abstract
Mobile and rapidly assembled structures play an important role in building temporary and semi-permanent accommodations and shelters in post-disaster management. One of the most efficient construction systems that can be used in rapidly assembled buildings is lightweight panelized systems. Use of rapidly assembled panelized systems is becoming very popular for cutting the construction time and transportation costs that make them suitable options for rapid assembly construction. In addition, when acoustic and thermal insulation of buildings is important, foam filled composite sandwich panels are an effective solution. Soft, semi-rigid and rigid Polyurethane (PU) foams, which are first...
Discussion of “rocking vibration of a rigid disk embedded in any depth of a coupled seawater-visco-poro-elastic seabed half-space”
, Article Soil Dynamics and Earthquake Engineering ; Volume 104 , 2018 , Pages 449-450 ; 02677261 (ISSN) ; Samea, P ; Eskandari, M ; Sharif University of Technology
Elsevier Ltd
2018
First order decoupling of equations of motion formultibody systems consisting of rigid and elastic bodies
, Article Iranian Journal of Science and Technology, Transaction B: Technology ; Volume 24, Issue 3 , 2000 , Pages 342-343 ; 03601307 (ISSN) ; Fahimi, F ; Sharif University of Technology
2000
Abstract
An improved method for deriving elastic generalized coordinates is considered and Kane's equations of motion for multibody systems consisting of an arbitrary number of rigid and elastic bodies are presented. The equations are in general form and are applicable for any desired holonomic system. Flexibility in choosing generalized speeds in terms of generalized coordinate derivatives in Kane's method is used. It is shown that proper choice of a congruency transformation between generalized coordinate derivatives and generalized speeds leads to first order decoupled equations of motion for holonomic multibody systems consisting of an arbitrary number of rigid and elastic bodies. In order to...
A modified unsteady-nonlinear aeroelastic model for flapping wings
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; 2022 ; 09544100 (ISSN) ; Zare, H ; Bighashdel, A ; Sharif University of Technology
SAGE Publications Ltd
2022
Abstract
A novel integrated aeroelastic model of flapping wings (FWs) undergoing a prescribed rigid body motion is presented. In this respect, the FW nonlinear structural dynamics is enhanced via a newly proposed modification of implicit condensation and expansion (MICE) method that better considers the structural nonlinear effects. In addition, the unsteady aerodynamic model is also an extension of the widely utilized modified strip theory (MST) in which the flexibility effects are accounted for (MST-Flex). The integrated utility of the proposed generalized MICE and MST-Flex is demonstrated to be more realistic for elastic FW flight simulation applications. The prescribed rigid body motion is...
Image Registration Using a Total Variation Based Similarity Metric
, Ph.D. Dissertation Sharif University of Technology ; Manzouri Shelmani, Mohammad Taghi (Supervisor)
Abstract
Image registration is one of the fundamental and essential tasks for medical imaging and remote sensing applications. One of the most common challenges in this area is the presence of complex spatially varying intensity distortion in the images. The widely used similarity metrics, such as MI (Mutual Information), CC (Correlation Coefficient), SSD (Sum of Square Difference), SAD (Sum of Absolute Difference) and CR (Correlation Ratio), are not robust against this kind of distortion; because stationarity assumption and the pixel-wise independence cannot be obeyed and captured by these metrics. In this research, we proposed a new intensity-based method for simultaneous image registration and...
Terminal retrograde turn of rolling rings
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 3 , September , 2015 ; 15393755 (ISSN) ; Sarebangholi, M. S ; Alam, M. R ; Sharif University of Technology
American Physical Society
2015
Abstract
We report an unexpected reverse spiral turn in the final stage of the motion of rolling rings. It is well known that spinning disks rotate in the same direction of their initial spin until they stop. While a spinning ring starts its motion with a kinematics similar to disks, i.e., moving along a cycloidal path prograde with the direction of its rigid body rotation, the mean trajectory of its center of mass later develops an inflection point so that the ring makes a spiral turn and revolves in a retrograde direction around a new center. Using high speed imaging and numerical simulations of models featuring a rolling rigid body, we show that the hollow geometry of a ring tunes the rotational...
Design and Prototyping of an Attitude Control System for Rigid Bodies
, M.Sc. Thesis Sharif University of Technology ; Jalali, Mir Abbas (Supervisor)
Abstract
Attitude control of rigid bodies is a complicated but attractive problem in dynamics. One of its main practical applications is in satellite attitude control and specifically in space telescope orientation control. Using fuel thrusters is not only expensive in most cases, but also it cannot be considered as an appropriate solution from reliability and economic aspects in long-term applications such as space telescopes and telecommunication satellites. On the other hand, magnetic torquers and momentum wheels cannot be utilized for rapid and large maneuvers due to their inability in generating large torques, which are needed in such maneuvers. As a result, another type of attitude control...
Utilising flags to reduce drag around a short finite circular cylinder
, Article Journal of Turbulence ; Volume 19, Issue 3 , 2018 , Pages 229-251 ; 14685248 (ISSN) ; Kiani, F ; Tahaye Abadi, M ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
This paper utilises flags to decrease the drag around a short finite circular cylinder. Wall-adapted large eddy simulation and two-way fluid–structure interaction methods were applied to resolve unsteady turbulent flow structure. The far-field Reynolds number of the current configuration based on the cylinder diameter was chosen to be 20,000. In addition, the length-to-diameter ratio of the cylinder was assumed to be L/D = 2 whereas the flexible flag had a width-to-diameter ratio of W/D = 1.5. The results were compared with the regular short finite circular cylinder and the rigid flagged cylinder in our previous work. The results indicate that utilising flags inside the near-wake region of...
A simple method for analysis of sliding structures considering variations of friction coefficient
, Article Journal of Earthquake Engineering ; Volume 4, Issue 2 , 2000 , Pages 233-250 ; 13632469 (ISSN) ; Hamidi, M ; Ahmadi, G ; Sharif University of Technology
2000
Abstract
In this paper, the responses of multidegree of freedom (MDOF) structures on sliding foundations, subjected to harmonic or random base motions, are investigated taking into consideration the variations of friction forces. The variation of friction force is a consequence of variation of friction coefficient, which depends on such parameters as relative velocity and the existing pressure. Modelling of the friction force under the foundation raft is accomplished by using a fictitious rigid link with a rigid-perfectly plastic material. This results in identical equations of motion for the sliding structure, both in the sliding and nonsliding (stick) phases and considerably decreases the required...
On the assessment of modal nonlinear pushover analysis for steel frames with semi-rigid connections
, Article Structural Engineering and Mechanics ; Volume 32, Issue 3 , 2009 , Pages 383-398 ; 12254568 (ISSN) ; Mofid, M ; Sharif University of Technology
2009
Abstract
Applying nonlinear statistical analysis methods in estimating the performance of structures in earthquakes is strongly considered these days. This is due to the methods' simplicity, timely lower cost and reliable estimation in seismic responses in comparison with time-history nonlinear dynamic analysis. Among nonlinear methods, simplified to be incorporated in the future guidelines, Modal Pushover Analysis, known by the abbreviated name of MPA, simply models nonlinear behavior of structures; and presents a very proper estimation of nonlinear dynamic analysis using lateral load pattern appropriate to the mass. Mostly, two kinds of connecting joints, 'hinge' and 'rigid', are carried out in...
Coarse Grained Molecular Dynamics Simulation of DNA Nanomechanics
, Ph.D. Dissertation Sharif University of Technology ; Ejtehadi, Mohammad Reza (Supervisor) ; Khoei, Amir Reza (Co-Advisor)
Abstract
DNA is the most important biological molecule which contains all the genetic information of living organisms. The mechanical behavior of this molecule has a significant role on its functions. In this study, we introduce a model to for DNA nanomechanics. This model is called rigid base-pair chain in which every base pair is considered as a rigid object. The base-pairs only interact with their nearest neighbors via a harmonic potential. We have used this model to study the nanomechanical behavior of the DNA such as its bending, twisting, and stretching elasticity. Also the model was successful to predict the structure of DNA minicircles with extra amount of twist. After that we used the model...
The Effect of Hydrophobic Mismatch and Rigidity of Protein on the Cluster Formation of Transmembrane Proteins in Biomembranes
, M.Sc. Thesis Sharif University of Technology ; Ahmadiyan, Mohammad Taghi (Supervisor) ; Jalali, Mir Abbas (Co-Advisor) ; Khoshnood, Atefeh (Co-Advisor)
Abstract
Membrane proteins aggregation is a very important biological phenomenon in a variety of cell functions. It has been suggested that aggregation behavior of membrane proteins is influenced by the shape of the hydrophobic domain of the proteins, proteins hydrophobic mismatch and bilayer curvature. However, in this study by means of coarse grained membrane simulations it has been found that in thermal equilibrium, protein-protein interactions also depend on protein rigidity and structural strength. Based on simulation results, we have observed stable large clusters even in the absence of hydrophobic mismatch between lipids and proteins. Interestingly, our results also indicate that proteins with...
Sandwich beam model for free vibration analysis of bilayer graphene nanoribbons with interlayer shear effect
, Article Journal of Applied Physics ; Vol. 115, issue. 17 , May , 2014 ; ISSN: 00218979 ; Shokrollahi, H ; Hosseini-Hashemi, S ; Sharif University of Technology
Abstract
In this study, sandwich beam model (SM) is proposed for free vibration analysis of bilayer graphene nanoribbons (BLGNRs) with interlayer shear effect. This model also takes into account the intralayer (in-plane) stretch of graphene nanoribbons. The molecular dynamics (MD) simulations using the software LAMMPS and Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential are done to validate the accuracy of the sandwich model results. The MD simulation results include the two first frequencies of cantilever BLGNRs with different lengths and two interlayer shear moduli, i.e., 0.25 and 4.6GPa. These two interlayer shear moduli, 0.25 and 4.6GPa, can be obtained by sliding a small...
Automatic B-spline image registration using histogram-based landmark extraction
, Article 2012 IEEE-EMBS Conference on Biomedical Engineering and Sciences, IECBES 2012 ; 2012 , Pages 1004-1008 ; 9781467316668 (ISBN) ; Abbasi Asl, R ; Ghaffari, A ; Fatemizadeh, E ; Sharif University of Technology
2012
Abstract
Recognition and correction of inhomogeneous displacement caused by patient's movement has been recently discussed as an interesting topic in medical image processing. Considering consistency in general structure of the image during distortion, histogram could be employed as a fast implementation method in feature domain. Accordingly, attribute vectors could be defined for each pixel based on spatial features to find corresponding points in two images. Consequently a point-based and non-rigid transformation approach will be designed. A B-spline image registration has been applied to match those pairs with a defined smoothness factor. This algorithm is a step-by-step registration process...
Two-dimensional symmetric double contacts of elastically similar materials
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 230, Issue 10 , 2016 , Pages 1626-1633 ; 09544062 (ISSN) ; Adibnazari, S ; Sharif University of Technology
SAGE Publications Ltd
2016
Abstract
The two-dimensional contact problem for an elastic body indenting an elastically similar half plane resulting in double contacts is important for various applications. In this paper, a generic quasi-static two-dimensional symmetric double contact problem with nonsingular end points between two elastically similar half planes, under the constant normal and oscillatory tangential loading, is analyzed. The classical singular integral equations approach is utilized to extract the pressure and shear functions in the contact zones; subsequently boundary conditions at end points are applied and a new side condition is derived and titled "the consistency condition" for symmetric double contacts....
A predictor-based attitude and position estimation for rigid bodies moving in planar space by using delayed landmark measurements
, Article Robotica ; 2016 , Pages 1-16 ; 02635747 (ISSN) ; Namvar, M ; Sharif University of Technology
Cambridge University Press
Abstract
This paper proposes a globally and exponentially convergent predictive observer for attitude and position estimation based on landmark measurements and velocity (angular and linear) readings. It is assumed that landmark measurements are available with time-delay. The maximum value of the sensor delay under which the estimation error converges to zero is calculated. Synthesis of the observer is based on a representation of rigid-body kinematics and sensor delay, formulated via ordinary and partial differential equations (ODE-PDE). Observability condition specifies necessary and sufficient landmark configuration for convergence of attitude and position estimation error to zero. Finally, for...