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Temperature dependence study of nonocontact AFM images using molecular dynamics simulations [electronic resource]
, Article Int. Journal of Modern Physics ; 2012, Vol. 5, pp. 418-432 ; Meghdar, Ali ; Sharif University of Technology
Abstract
The effect of temperature on the noncontact atomic force microscopy (NC-AFM) surface imaging is investigated with the aid of molecular dynamics (MD) analysis based on the Sutton-Chen (SC) interatomic potential. Particular attention is devoted to the tip and sample flexibility at different temperatures. When a gold coated probe is brought close to the Au (001) surface at high temperatures, the tip and surface atoms are pulled together and their distance becomes smaller. The tip and sample atoms displacement varies in the different environment temperatures and this leads to the different interaction forces. Along this line, to study the effect of temperature on the resulting images, we have...
Molecular Dynamics Simulation of the Dynamic Behavior of Nanoresonators
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
In this project, the equilibrium structure of clamped-free silicon nano-beams is investigated using molecular dynamics (MD) simulations. Four main interatomic potentials for silicon nanostructures, i.e. Tersoff, MEAM, Stillinger-Weber and EDIP, are implemented in the current study. Using aforementioned potentials, the structural stability of Si nano-beams are studied and effects of thickness, width, length, size, lattice direction, facets of cross section, and temperature on the equilibrium structure of nano-beams are investigated. The conducted simulations demonstrate that equilibrium structure of nano-beam is completely dependent on the type of atomic potential used for modeling....
Modeling of Force Interactions between Tip of Atomic Force Microscopy in Trolling Mode and Environment
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Submerging of the Micro-beam of the AFM is indispensible in case of imaging bio-samples. (Bio-samples are unstable in non-aquos environment.), so hydrodynamical interaction of liquid and beam (viscous and meniscus forces) will result into quality factor decrease. This will cause image resolution decrement as well as damage to the sample because of large tip-sample forces during imaging of the bio-samples. The proposed method “Trolling mode AFM” keeps the micro-beam of the AFM out of the liquid, by adding a nano-needle to the end of the AFM tip. This would lead to resolve the aforementioned problems. Modeling of a part of the operation of this mechanism was done in this thesis, in order to...
A Fabrication Method of Neutrally-buoyant Magnetic Micro-robot to Improve Its Motion Control
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Micro-robotics is one of the currently emerging technologies which has attracted attentions for its probable applications in different fields including biotechnology, diagnosis and treatment in medical engineering as well as general studies in micro-scale science and engineering. Magnetic micro-robotics is considered as the most promising group, primarily due to the biocompatibility of magnetic fields and advances in electronic circuits to produce and control such fields. One critical point in utilizing these robots is their high density in comparison with the working fluid and their tendency to sink. In this thesis, a method to fabricate buoyant magnetic robots has been proposed based on...
Completion of Electromagnetic System and Design of Robust Controller to Control the Movement of Micro-robots in Three-Dimensional Space
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Today, the need to access very small environments is felt in various medical, industrial, biological and military fields. Due to their small size, microrobots have the ability to perform tasks that would be very difficult to do on a larger scale, but this ability of microrobots makes feeding and controlling them challenging. There are several methods for providing power and control of microrobots, which include their internal or external stimulation, among which the magnetic stimulation method is used in this research, which does not cause damage to body tissues.In this thesis, an electromagnetic system with nine cylindrical coils is used to control the three-dimensional movement of magnetic...
Dynamic Modeling and Localization of a Moving Magnetic Particle in a Fluid for Capsule Endoscopy Application
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Endoscopy is a medical operation in which a camera is sent into the patient's body and the physician starts taking pictures at specified times. In the traditional endoscopic procedure, a camera is sent into the body by a guiding wire. This can cause severe pain to the patient. In the newer method, a camera is mounted on a small capsule and the patient swallows the capsule. Then the camera inside the capsule starts taking photos and sends them out. This procedure, in addition to being painless, allows the physician to access the innermost parts of the body or the digestive tract.In capsule endoscopy, unlike the older method, one has to find the position and orientation of the capsule at any...
Modeling, Localization and Control of Endoscopic Capsule for Tissue Biopsy
,
M.Sc. Thesis
Sharif University of Technology
;
Nejat Pishkenari, Hossein
(Supervisor)
Abstract
Nowadays, endoscopic capsules are an interesting technique due to their ability to minimize patient discomfort and provide access to all parts of the gastrointestinal tract. However, they lack some capabilities of traditional methods, such as performing biopsies. An essential requirement for performing a biopsy of a specific part of the gastrointestinal tract is capsule control; in addition, localization information is required for closed-loop control. The goal of this research is the localization and control of a capsule with a biopsy module. For this purpose, an endoscopic capsule using the concept of a magnetic spring was introduced, which had different magnets so its localization and...
Modeling of the Flexible Instrument Inside the Vascular Environment for Its Motion Control in Minimally Invasive Procedures
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Minimally invasive procedures are diagnostic or therapeutic methods that cause minimal injuries and side effects for patients. PCI is a common minimally invasive procedure for diagnosis and curing of cardiovascular disorders. In this procedure, the surgeon can have access to the cardiac vessels by a flexible instrument. However, motion control of this instrument inside the patient's body relies on surgeon's skills and in some cases, is time consuming so that the toxic effects of radiation on patient and surgical team increases. Magnetic flexible instruments are suggested to address this problem. Nevertheless, motion control of the flexible instrument inside the body still has many challenges...
Robust adaptive backstepping control of uncertain lorenz system [electronic resource]
, Article Journal of American Institute of Physics ; 2010, Vol. 20, pp. 1-5 ; Jalili, Nader ; Mahboobi, Seyed Hanif ; Alasty, Aria ; Meghdari, Ali ; Sharif University of Technology
Abstract
In this paper, a novel robust adaptive control method is proposed for controlling the Lorenz chaotic attractor. A new backstepping controller for the Lorenz system based on the Lyapunov stability theorem is proposed to overcome the singularity problem that appeared in using the typical backstepping control method. By exploiting the property of the system, the resulting controller is shown to be singularity free and the closed loop system is globally stable. Due to unavailability of system states measurement in practice, the controller is selected such that only one system state is needed. To overcome the problem of parameter uncertainty, an additional term to Lyapunov function is added and...
Simulation of imaging in tapping-mode atomic-force microscopy: a comparison amongst a variety of approaches
, Article Journal of Physics D: Applied Phyics ; Vol.44, Number 7, p.1-9, 2011 ; Mahboobi, S. H ; Meghdari, A. (Ali) ; Sharif University of Technology
Abstract
Models capable of accurate simulation of microcantilever dynamics coupled with complex tip–sample interactions are essential for interpretation and prediction of the imaging results in amplitude modulation or tapping-mode atomic-force microscopy (AM-AFM or TM-AFM). In this paper, four approaches based on combinations of lumped and finite element methods for modelling of cantilever dynamics, and van der Waals and molecular dynamics for modelling of tip–sample interactions, are used to simulate the precise imaging by AM-AFM. Based on the simulated imaging and force determination, the efficiency of different modelling schemes is evaluated. This comparison is performed considering their...
Study and Simulation of Nanoparticles Translocation through Cell Membrane
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
In this research, we aim to study and simulate how nanoparticels translocate through cell membrane. For this purpose, at first a gold nanoparticle is selected as the drug carrier. The partial charges of the ligands are calculated using quantum mechanics based on HF technique with 6-31Gd basis set. To have a realistic shape for nano drug, number and arrangement of ligands are determined based on optimization. After all atom simulations and comparison of results such as diffusion coefficient with experiments, a coarse-grained model of these drugs is created and put inside solvent beside a membrane. The cytoplasmic membrane includes more than 60 types of phospholipids like animal membranes....
Design and Fabrication of a XY Nano-Positioning System
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Nanopositioning is technology of positioning & manipulation of Nano-scale object. This technology can be considered as one of the fundamental necessities in Nano & Micro research and fabrication and made lots of unbelievable advancement in researches and technologies. There are lots of mechanical systems designed for large scale positioning with sub millimeter resolution, but when it’s come to Nano scale, the range of access should be limited to some micrometer. Also in Nano-scale motion some difficulties like backlash, stick-slip and friction is phenomenon. For increasing the workspace using coarse and fine positioning systems may be an appropriate method. In this method a fine positioning...
Design of a Control System Based on the Permanent Magnet for Control of a Magnetic Catheter
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Currently, the use of robots and microrobots in medical applications has significantly increased due to their extensive and unique capabilities. One such application involves the utilization of magnetic continuum robots controlled by an external magnetic field in minimally invasive surgeries. This research focuses on discussing methods for effectively controlling magnetic-continuum robots and applying external magnetic fields. Two primary methods for applying the external magnetic field are explored: the use of electromagnetic coils and permanent magnets. Based on these methods, systems for applying the field and controlling the magnetic continuum robot have been constructed and...
Localization of Magnetic Catheter Tip Using an Array of Magnetic Sensors
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Minimally invasive surgery is highly valued mainly due to the reduction of the patient’s recovery period. Catheters are among the most important tools in minimally invasive surgeries. Catheter is a flexible tool that has the ability to pass through difficult paths. In common localization methods, fluoroscopy is used to determine the position of the catheter’s tip. One main disadvantage of this method is that it is very dangerous for therapists who are exposed to X-ray radiation for long periods of time. A magnetic catheter is created by adding a magnet to the end of the catheter. The possibility of guiding magnetic catheter by an external magnetic field, controlling the applied force and...
Design and Fabrication of An Electromagnetic Actuation System for Generation of Desired Magnetic Field and Control of Magnetic Particles
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Being harmless to living tissues makes magnetic robots very promising for medical applications. Furthermore, since these robots are driven by external magnetic fields, no actuators are needed to be placed on the robots, enabling them to come in very small dimensions if necessary. Motion control of small magnetic particles paves the way for future applications, such as deliberate drug-delivery, sampling, and lowinvasive surgeries.The goal of this research is to design and construct a platform for generating desired magnetic fields in order to control the motion of magnetic robots in threedimensional space. In order to do so, a system of eight electromagnetic coils with iron cores was built....
Satellite attitude PDE-based controller design considering fluid fuel sloshing in planar maneuver
, Article Aerospace Science and Technology ; Volume 122 , 2022 ; 12709638 (ISSN) ; Salarieh, H ; Nejat Pishkenari, H ; Sharif University of Technology
Elsevier Masson s.r.l
2022
Abstract
Due to significance of high-accuracy attitude control, the fuel sloshing effects on the satellite attitude should be considered, more precisely. This work deals with the attitude control of a liquid propellant-filled satellite considering the incompressible fuel sloshing in the planar maneuver. The satellite consists of a rigid body, a partially-filled tank and a flexible diaphragm. Hamilton's principle is employed to derive nonlinear coupled PDEs-ODEs governing the coupled satellite-diaphragm propellant tank system. Afterwards, to dispense with the spillover instability, a PDE-based controller is designed to realize the satellite attitude control while tracking a desired pitch angle and...
Observer-based boundary feedback control for attitude tracking of rigid bodies with partially liquid-filled cavities
, Article Aerospace Science and Technology ; Volume 132 , 2023 ; 12709638 (ISSN) ; Salarieh, H ; Nejat Pishkenari, H ; Sharif University of Technology
Elsevier Masson s.r.l
2023
Abstract
In the attitude tracking control tasks of rigid bodies with partially filled cavities, liquid sloshing is a crucial characteristic that hinders effective controller design and accuracy improvement. To overcome this problem, we propose a novel boundary feedback control (BFC) scheme based on the PDE-ODE cascade governing the rigid body attitude and internal liquid dynamics. We further develop an innovative PDE-based observer to cope with requirements on the infinite number of unmeasurable boundary states. Thus, using only attitude data, the discussed boundary controller can stabilize the attitude tracking error and the infinite-dimensional internal dynamics. The asymptotic stability of the...
Simulations of surface defects characterization using force modulation atomic force microscopy
, Article Proceedings of the ASME Design Engineering Technical Conference, 30 August 2009 through 2 September 2009, San Diego, CA ; Volume 6 , 2009 , Pages 681-687 ; 9780791849033 (ISBN) ; Meghdari, A ; Sharif University of Technology
2009
Abstract
This paper is devoted to the characterization of the surface defects using a recently developed AFM technique named as frequency and force modulation AFM (FFM-AFM). The simulated system includes a recently developed gold coated AFM probe which interacts with a sample including single-atom vacancy and impurities. In order to examine the behavior of the above system including different transition metals, molecular dynamics (MD) simulation with Sutton-Chen (SC) interatomic potential is used. Along this line, an imaging simulation of the probe and sample is performed, and the effects of the horizontal scan speed, the effective frequency set-point, the cantilever stiffness, the tip-sample rest...
Simulation of Imaging in Trolling Mode Atomic Force Microscopy by Molecular Dynamics Method
, M.Sc. Thesis Sharif University of Technology ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Atomic force microscopy (AFM), as an indispensable tool for nanoscale characterization, has major drawback for operation in a liquid environment arising from the large hydrodynamic drag on the vibrating cantilever. The newly introduced “Trolling Mode” (TR-Mode) AFM resolves this complication utilizing a specialized nanoneedle cantilever that keeps the cantilever outside of the liquid. Herein, a mechanical model with a lumped mass was developed to capture the dynamics of such cantilever with a nanoneedle tip. This new developed model was applied to investigate the effects of the needle – liquid interface on the performance of the AFM, including the imaging capability in liquid. Also...
Design, Fabrication and Hovering Control of a Quadrotor Aerial Vehicle
, M.Sc. Thesis Sharif University of Technology ; Meghdari, Ali (Supervisor) ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
One of the most significant aerial vehicles which has been subject of study of so many engineers and students is quadrotor or quadcopter, which is a cross sectional configuration of motors and propellers. This aerial robot is controlled through slight differences between the angular velocities of the four motors, and robot dynamics is completely nonlinear, thus sophisticated control algorithms are needed. The aim of this project consists of design, fabrication and control of a quadrotor capable of stable hovering. First, some preliminary decisions about general charachteristics of the robot were made. According to these decisions, other mechanical parts were designed and fabricated. Then,...