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Comments on “Hydroelastic impact of a horizontal floating plate with forward speed” [J. Fluids Struct. 60 (2016) 97–113]
, Article Journal of Fluids and Structures ; Volume 81 , 2018 , Pages 378-382 ; 08899746 (ISSN) ; Rahbar Ranji, A ; Haddadpour, H ; Sharif University of Technology
Academic Press
2018
Abstract
This comment concerns the mathematical errors in the recent work of Wang et al. (2016). The corrected equations are presented. Deflections and critical values of compressive force and forward speed are modified. © 2018 Elsevier Ltd
Chaos control in continuous mode of T-AFM systems using nonlinear delayed feedback via sliding mode control
, Article ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, Seattle, WA, 11 November 2007 through 15 November 2007 ; Volume 11 PART A , 2008 , Pages 201-208 ; 079184305X (ISBN); 9780791843055 (ISBN) ; Salaried, H ; Alasty, A ; Sharif University of Technology
2008
Abstract
The taping mode Atomic Force Microscopic (T-AFM) can be assumed as a cantilever beam which its base is excited by a sinusoidal force and nonlinear potential interaction with sample. Thus the cantilever may cause chaotic behavior which decreases the performance of the sample topography. In order to modeling, using the galerkin method, the PDE equation is reduced to a single ODE equation which properly describing the continuous beam. In this paper a nonlinear delayed feedback control is proposed to control chaos in T-AFM system. Assuming model parameters uncertainties, the first order Unstable Periodic Orbits (UPOs) of the system is stabilized using the sliding nonlinear delayed feedback...
Effects of soft marine fouling on wave-induced forces in floating aquaculture cages: Physical model testing under regular waves
, Article Ocean Engineering ; Volume 238 , 2021 ; 00298018 (ISSN) ; Zeinoddini, M ; Aalami Harandi, M. M ; Abi, F. A ; Jadidi, P ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Previous experiments on the fouling/current and fouling/wave interactions were mostly limited to two dimensional (2D) net panels or isolated twines. The current paper deals with the wave-induced forces/moments in three dimensional (3D) physical models of a gravity net-cage. The colonial hydroid Ectopleura larynx, a common fouling organism in the aquaculture industry, was artificially modelled and considered in the current experiments. A clean cage and cages with different fouling lengths were tested under deep-water regular wave trains. The time series of the wave-induced forces/moments in the surge, sway, roll and pitch degrees of freedom were recorded and analysed. The experimental results...
The Problom of Forcing Number of Perfect Matching
, M.Sc. Thesis Sharif University of Technology ; Mahmoodian, Ebadollah (Supervisor) ; Ebrahimi Borogerdi, Javad (Supervisor)
Abstract
The notions of forcing edge and the forcing number of a perfect matching first appeared in 1991 by Harary, Klein and Živković. The root of these concepts can be traced to the works by Randić and Klein in 1985-1987, where the forcing number was introduced under the name of “innate degree of freedom” of a Kekulé structure, which plays an important role in the resonance theory in chemistry. Over the past three decades, more research has been done on the forcing set of perfect matchings. Here, we introduce bounds on the forcing number of perfect matching of some graphs that have already been known. Then, we extend the concept of forcing to fractional perfect matching and we introduce fractional...
Seismic Demands on Gravity Only Steel Frames
,
M.Sc. Thesis
Sharif University of Technology
;
Maleki, Shervin
(Supervisor)
Abstract
Nowadays, using perimeter steel moment frames in combination with interior gravity frames have become common practice in structural building design. One of the key benefits of this system is the open space that it provides for the architects. In active seismic regions, special details are required in the design of the seismic force resisting systems to make these frames ductile. However, these details cause excessive displacement for the gravity force resisting system. Although the gravity frames are not designed to endure seismic forces, they collaborate in the system’s response as they are connected to the same floor diaphragm and withstand lateral displacements. Therefore, these systems...
Vibration analysis of delaminated Timoshenko beams under the motion of a constant amplitude point force traveling with uniform velocity
, Article International Journal of Mechanical Sciences ; Volume 70 , 2013 , Pages 39-49 ; 00207403 (ISSN) ; Jafari Talookolaei, R. A ; Ahmadian, M. T ; Sharif University of Technology
2013
Abstract
A composite beam with single delamination traveled by a constant amplitude moving force is modeled accounting for the Poisson's effect, shear deformation and rotary inertia. The mechanical behavior between the delaminated surfaces is modeled using a piecewise-linear spring foundation. The governing differential equations of motion for such system are derived. Primarily, eigen-solution technique is used to obtain the natural frequencies and their corresponding mode shapes of such beam. Then, the Ritz method is employed to derive the dynamic response of the beam due to the moving force. The obtained results for the free and forced vibrations of beams are verified against reported similar...
Force controlled manipulation of biological cells using a monolithic MEMS based nano-micro gripper
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 2 , 2012 , Pages 193-201 ; 9780791845189 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
Nano-micro grippers are able to pick-transport-place the micro or nanometer -sized materials, such as manipulation of biological cells or DNA molecules in a liquid medium. This paper proposes a novel monolithic nano-micro gripper structure with two axis piezoresistive force sensor which its resolution is under nanoNewton. The results of the study have been obtained by the simulation of the proposed gripper structure in Matlab software. Motion of the gripper arm is produced by a voice coil actuator. The behavior of the cell has been derived using the assumptions in the literatures. Moreover, two simple PID controllers, one for control of the gripper motion and another for control of the force...
Kinematics and force analysis of a 6 degrees of freedom 3-UPS mechanism with triangular platform for haptic applications
, Article International Conference on Control, Automation and Systems ; 2012 , Pages 694-698 ; 15987833 (ISSN) ; 9781467322478 (ISBN) ; Sadeghpour, M ; Hassanpour, S ; Vossoughi, G ; Sharif University of Technology
2012
Abstract
This paper presents inverse dynamics equations for a 3-UPS mechanism using virtual work principle. This mechanism has three UPS legs connecting the base to a triangular platform. By changing the orientation of leg's actuators a non-symmetric mechanism with a suitable workspace near the origin without any singularity is obtained. Direct and inverse kinematics Jacobian matrices of the mechanism are obtained by the Newton-Euler approach. Then the inverse dynamics problem is solved using the principle of virtual work, so that the force and torque of active actuators have been obtained by having external forces (force and torque) acted on the platform. Force analysis of the 3-UPS mechanism has...
Atomic interactions between metallic tips and surfaces in NC-AFM
, Article Journal of Physics D: Applied Physics ; Volume 48, Issue 12 , February , 2015 ; 00223727 (ISSN) ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
In this paper, the atomic-scale interactions between metallic tips and samples in noncontact atomic force microscopy (NC-AFM) are studied using molecular dynamics simulations. The effects of the tip and sample materials, the surface plane direction and the lateral position of the tip with respect to the sample, on the interaction force and the dissipated energy, are investigated. The simulations conducted demonstrate that, generally, we can classify the possible outcomes for the dynamics due to the tip-surface interactions into four major categories. The first category includes all cases in which there are no considerable instabilities in tip-surface interactions, leading to negligible...
Investigation of the size-dependent dynamic characteristics of atomic force microscope microcantilevers based on the modified couple stress theory
, Article International Journal of Engineering Science ; Volume 48, Issue 12 , 2010 , Pages 1985-1994 ; 00207225 (ISSN) ; Asghari, M ; Rahaeifard, M ; Ahmadian, M. T ; Sharif University of Technology
Abstract
In this paper, the resonant frequency and sensitivity of atomic force microscope (AFM) microcantilevers are studied using the modified couple stress theory. The classical continuum mechanics is incapable of interpreting micro-structure-dependent size effects when the size of structures is in micron- and sub-micron scales. However, this dependency can be well treated by using non-classical continuum theories. The modified couple stress theory is a non-classic continuum theory which employs additional material parameters besides those appearing in classical continuum theory to treat the size-dependent behavior. In this work, writing differential equations of motion of AFM cantilevers together...
Sub-pixel image registration based on physical forces
, Article 2010 International Conference on Wireless Communications and Signal Processing, WCSP 2010, 21 October 2010 through 23 October 2010, Suzhou ; 2010 ; 9781424475551 (ISBN) ; Ghorbani, S ; Beheshti Shirazi, A. A ; Sharif University of Technology
2010
Abstract
A new method for image registration has been previously proposed by the authors, which the registration is based on physical forces. The registration parameters are translation and rotation. This method assumes images like charged materials that attract each other. In this case, one of the images moves in the same direction as the applied force while the other one is still. The movement of the image continues until the resultant force becomes zero. This approach estimates the registration parameters simultaneously and leading to a better optimized set of registration parameters. The registration error for this method is 1 to 3 pixels. In this paper we aim to develop this method for the...
Detection of ammonia gas by knudsen thermal force in micro gas actuator
, Article Case Studies in Thermal Engineering ; Volume 12 , 2018 , Pages 276-284 ; 2214157X (ISSN) ; Barzegar Gerdroodbary, M ; Mosavat, M ; Ganji, D. D ; Sharif University of Technology
Abstract
Direct Simulation Monte Carlo (DSMC) method is applied to evaluate the performance of a new micro gas sensor (MIKRA) for mass analysis of ammonia in the rarefied gas. In order to simulate a rarefied gas inside the micro gas detector, Boltzmann equation is applied to obtain high precision results. This study performed comprehensive studies to reveal the main mechanism of force generation and applied this for the analysis of the gas mixture. Our findings show that value of generated Knudsen force significantly varies when the percentage of the NH3 varies in the mixture. According to obtained results, the maximum Knudsen force increases when the fraction of the ammonia decreases. Our findings...
On the structural and strong structural controllability of undirected networks
, Article IEEE Transactions on Automatic Control ; Volume 63, Issue 7 , July , 2018 , Pages 2234-2241 ; 00189286 (ISSN) ; Haeri, M ; Mesbahi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Characterization of network controllability through its topology has recently gained a lot of attention in the systems and control community. Using the notion of balancing sets, in this note, such a network-centric approach for the controllability of certain families of undirected networks is investigated. Moreover, by introducing the notion of a generalized zero forcing set, the structural controllability of undirected networks is discussed; in this direction, lower bounds on the dimension of the controllable subspace are derived. In addition, a method is proposed that facilitates synthesis of structural and strong structural controllable networks as well as examining preservation of...
Designing instrumented walker to measure upper-extremity’s efforts: a case study
, Article Assistive Technology ; 2018 , Pages 1-9 ; 10400435 (ISSN) ; Arab Baniasad, M ; Arazpour, M ; Farahmand, F ; Zohoor, H ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
The high prevalence of shoulder pain in using walkers in patients who have spinal cord injury (SCI). Also, the limited options available to economically measure grip forces in walkers, which drove the need to create one. This article describes a method to obtain upper-extremities’ forces and moments in a person with SCI by designing an appropriate instrumented walker. First, since the commercial multidirectional loadcells are too expensive, custom loadcells are fabricated. Ultimately, a complete gait analysis by means of VICON motion analysis and using inverse dynamic method has been held to measure upper-extremities’ efforts. The results for a person with SCI using a two-wheel walker in low...
Designing instrumented walker to measure upper-extremity’s efforts: A case study
, Article Assistive Technology ; Volume 31, Issue 5 , 2019 , Pages 267-275 ; 10400435 (ISSN) ; Baniasad, M. A ; Arazpour, M ; Farahmand, F ; Zohoor, H ; Sharif University of Technology
Taylor and Francis Inc
2019
Abstract
The high prevalence of shoulder pain in using walkers in patients who have spinal cord injury (SCI). Also, the limited options available to economically measure grip forces in walkers, which drove the need to create one. This article describes a method to obtain upper-extremities’ forces and moments in a person with SCI by designing an appropriate instrumented walker. First, since the commercial multidirectional loadcells are too expensive, custom loadcells are fabricated. Ultimately, a complete gait analysis by means of VICON motion analysis and using inverse dynamic method has been held to measure upper-extremities’ efforts. The results for a person with SCI using a two-wheel walker in low...
vThe effect of saddle-assistive device on improving the gait parameters of patients with the lower limbs weakness: a pilot study
, Article Journal of Bionic Engineering ; Volume 17, Issue 6 , 2020 , Pages 1175-1185 ; Amini, S ; Farahmand, F ; Sharif University of Technology
Springer
2020
Abstract
To help walking, using assistive devices can be considered to reduce the loads caused by weight and to effectively decrease the propulsive forces. In this study, a mobility Saddle-Assistive Device (S-AD) supporting body weight while walking was evaluated on two healthy volunteers. This device is based on the support of body weight against gravity with the help of a saddle, which is not used in other passive mobility assistive devices. To prove the efficiency of this device, the experimental results obtained while walking with this device were compared with those related to walking without the assistive device. The results showed that this device could significantly reduce the forces and...
Closed-form solutions of the pull-in instability in nano-cantilevers under electrostatic and intermolecular surface forces
, Article International Journal of Solids and Structures ; Volume 44, Issue 14-15 , 2007 , Pages 4925-4941 ; 00207683 (ISSN) ; Alasty, A ; Akbari, J ; Sharif University of Technology
2007
Abstract
In this paper, a distributed parameter model is used to study the pull-in instability of cantilever type nanomechanical switches subjected to intermolecular and electrostatic forces. In modeling of the electrostatic force, the fringing field effect is taken into account. The model is nonlinear due to the inherent nonlinearity of the intermolecular and electrostatic forces. The nonlinear differential equation of the model is transformed into the integral form by using the Green's function of the cantilever beam. Closed-form solutions are obtained by assuming an appropriate shape function for the beam deflection to evaluate the integrals. The pull-in parameters of the switch are computed under...
Influence of the tip mass on the tip-sample interactions in TM-AFM
, Article Ultramicroscopy ; Volume 111, Issue 8 , Jul , 2011 , Pages 1423-1436 ; 03043991 (ISSN) ; Meghdari, A ; Sharif University of Technology
2011
Abstract
This paper focuses on the influences of the tip mass ratio (the ratio of the tip mass to the cantilever mass), on the excitation of higher oscillation eigenmodes and also on the tip-sample interaction forces in tapping mode atomic force microscopy (TM-AFM). A precise model for the cantilever dynamics capable of accurate simulations is essential for the investigation of the tip mass effects on the interaction forces. In the present work, the finite element method (FEM) is used for modeling the AFM cantilever to consider the oscillations of higher eigenmodes oscillations. In addition, molecular dynamics (MD) is used to calculate precise data for the tip-sample force as a function of tip...
Study and Development of Dual Porosity/Permeability Models for Simulation of Forced Gravity Drainage Mechanism in Fractured Porous Media
, M.Sc. Thesis Sharif University of Technology ; Massihi, Mohsen (Supervisor) ; Gerami, Shahab (Supervisor) ; Ganjeh Ghazvini, Mostafa (Co-Advisor)
Abstract
The available investigations show that gravity drainage mechanism in fractured reservoir make a high recovery factor in comparison with other mechanisms. In recent years, the forced gravity drainage assisted by gas injection is also introduced; despite of its importance there is no comprehensive modeling study in the literature. The fractured reservoir is simulated frequently by dual porosity models in which the transfer function is the key issue for this method of simulation. This study makes an effort by comparison of different transfer functions with fine grid simulation results of a single block model, in order to evaluate their ability for simulation of forced gravity drainage...
Pull-in Analysis of Nano/Micromirrors under Effect of Capillary Force with Consideration Influences of Casimir and Van Der Waals Forces
, M.Sc. Thesis Sharif University of Technology ; Zohoor, Hassan (Supervisor)
Abstract
In this thesis, pull-in of nano/micromirrors under effects of capillary, Casimir and van der Waals (vdW) forces is investigated based on two models. In the first model, only rotation of torsional beams of mirror is considered. In the second model, effect of bending of the torsional beams is also considered. The static behavior of the mirror under capillary, Casimir and vdW loading are also studied using these models. Results show that neglecting bending effect, can lead to considerable overestimation in predicting the pull-in limits of the nano/micromirrors under these forces.Results reveal that the static behavior of the nano/micromirrors under these forces highly depends on the...