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#### Investigation of Ising Model in Nano Systems with Long Range Interaction

, Ph.D. Dissertation Sharif University of Technology ; Parsafar, Gholam Abbas (Supervisor)
Abstract

Ising model in nano systems are studied, in the presence of a magnetic field. For a one-dimensional(1-D) array of spins interacting via nearest-neighbor and next-nearest-neighbor interactions we calculated the heat capacity , the surface energy, the finite-size free energy, and bulk free energy per site. The heat capacity versus temperature exhibited a common wide peak for systems of any size. A small peak also appears at lower temperatures for small arrays when the ratio of magnetic field- spin interaction energy over the nearest-neighbour spin-spin interaction energy f is within and size. The peak becomes smaller for longer array and eventually vanishes for long arrays, disappearing when...

#### Synthesis, Characterization and Application of Inorganic Nanosystems based on Biocompatible and Highly Tunable Materials for Targeted Delivery and Release of Gene and Drug

, Ph.D. Dissertation Sharif University of Technology ; Bagherzadeh, Mojtaba (Supervisor)
Abstract

In this dissertation, an attempt has been made to prepare a library from most of the inorganic and organic compounds in order to strengthen the use of nanosystems for the purpose of controlled delivery and release of drugs and genetic material. In this regard, a complete set of compounds based on metal nanoparticles, layered double hydroxides, metal-organic frameworks, graphene oxide and carbon nanotubes were designed, synthesized and characterized, and nanocomposites and hybrids of them based on palladium, zinc, copper and nickel were designed as well. The nano-stable system is designed with positive surface potential, very low cytotoxicity, biodegradability and acceptable environment as...

#### Molecular dynamics study of success evaluation for metallic nanoparticles manipulation on gold substrate

, Article Proceedings of the ASME Design Engineering Technical Conference, 30 August 2009 through 2 September 2009, San Diego, CA ; Volume 6 , 2009 , Pages 345-346 ; 9780791849033 (ISBN) ; Meghdari, A ; Jalili, N ; Sharif University of Technology
Abstract

Using molecular dynamics, the behavior of nanoparticles during manipulation process is investigated in this paper. The system consists of a tip, cluster and substrate. The focus of the present research is on ultra-fine metallic nanoclusters. The system of concern is made of different transition metals. Two criteria have been proposed for evaluation of success in a pushing process. Such criteria describe the intactness of nanoparticle/substrate pair. The effects of cluster material and manipulation speed on the success of the process are investigated by atomistic simulations. Such qualitative simulation studies can evaluate the level of success of manipulation regarding different working...

#### Stress distribtuion on open-ended carbon nanotubes

, Article 2008 Proceedings of the ASME - 2nd International Conference on Integration and Commercialization of Micro and Nanosystems, MicroNano 2008, 3 June 2008 through 5 June 2008, Kowloon ; 2008 , Pages 343-351 ; 0791842940 (ISBN); 9780791842942 (ISBN) ; Alasty, A ; Sharif University of Technology
2008

Abstract

The stress distribution on open-ended Carbon Nanotubes (CNTs) embedded in a composite material is considered in this work and an analytical solution for the stress distribution has been obtained. The effects of CNT's thickness and CNT's length on the distribution of stress have been investigated. To find the governing relations, continuity equations of the axisymmetric problem in cylindrical coordinate (r,o,z) are used. Under some assumptions, the governing equations are solved and by using constitutive equations and applying the boundary conditions, an equation which relates the stress applied to the representative volume element with the stress distribution on the CNT, has been found. The...

#### Applications of single-layered graphene sheets as mass sensors and atomistic dust detectors

, Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 11 , 2007 , Pages 99-104 ; 079184305X (ISBN) ; Ahmadian, M. T ; Vafai, A ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2007

Abstract

Molecular structural mechanics is implemented to model vibrational behavior of defect free single-layered graphene sheets (SLGSs) at constant temperature. To mimic these two-dimensional layers, zigzag and armchair models with cantilever and bridge boundary conditions are adopted. Fundamental frequencies of these nano structures are calculated, and it is perceived that they are independent of the chirality and aspect ratio. Effects of point mass and atomistic dust on the fundamental frequencies are also considered in order to investigate the possibility of using SLGSs as sensors. Results of exhibit the principle frequencies are highly sensitive to the added mass in the order of 10-6 fg....

#### Chaos control in single mode approximation of T-AFM systems using nonlinear delayed feedback based on sliding mode control

, Article 2007 Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference ; Volume 3 PART B , 2008 , Pages 725-730 ; ISBN: 9780791848043 ; Salarieh, H ; Arjmand, M. T ; Alasty, A ; Sharif University of Technology
Abstract

The taping mode Atomic Force Microscopic (T-AFM) can be properly described by a sinusoidal excitation of its base and nonlinear potential interaction with sample. Thus the cantilever may cause chaotic behavior which decreases the performance of the sample topography. In this paper a nonlinear delayed feedback control.is proposed to control.chaos in a single mode approximation of a 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 control. The effectiveness of the presented methods is numerically verified and the results show the high performance of the control.er

#### Peculiar transport properties in Z-shaped graphene nanoribbons: A nanoscale NOR gate

, Article Thin Solid Films ; Volume 548 , 2013 , Pages 443-448 ; 00406090 (ISSN) ; Khoeini, F ; Shokri, A ; Sharif University of Technology
2013

Abstract

A nanoscale logic NOR gate has been theoretically designed by magnetic flux inputs in a Z-shaped graphene nanoribbon composed of an armchair ribbon device sandwiched between two semi-infinite metallic zigzag ribbon leads. The calculations are based on the tight-binding model and iterative Green's function method, in which the conductance as well as current-voltage characteristics of the nanosystem are calculated, numerically. We show that the current and conductance are highly sensitive to both the magnetic fluxes subject to the device and the size of the system. Our results may have important applications for building blocks in the nanoelectronic devices based on graphene nanoribbons

#### The oscillatory behavior of doubly clamped microgyroscopes under electrostatic actuation and detection

, Article Proceedings of the ASME Design Engineering Technical Conference ; Volume 1 , 2013 ; 9780791855843 (ISBN) ; Firoozbakhsh, K ; Ahmadian, M. T ; Computers and Information in Engineering Division; Design Engineering Division ; Sharif University of Technology
American Society of Mechanical Engineers
2013

Abstract

In MEMS gyroscopes, it is essential to use matched resonance frequencies of the drive and sense vibrational modes for improving the sensitivity. For this end, the natural frequencies can be tuned by voltages. In this study, a new model is utilized to determine the natural frequencies of the doubly clamped beam microgyroscope. In the model, nonlinear electrostatic forces, fringing fields and mid-plane stretching of thebeam are considered. The system is actuated and sensed by electrostatic force and its natural frequencies and stiffness are detuned by DC voltages. The oscillatory problem of the gyroscope is analytically solved versus DC voltages for different design parameters. Copyright

#### A coupled two degree of freedom model for nano/micromirrors under van der waals force

, Article Proceedings of the ASME Design Engineering Technical Conference ; Volume 5 , 2012 , Pages 145-150 ; 9780791845042 (ISBN) ; Darvishian, A ; Ahmadian, M. T ; Sharif University of Technology
2012

Abstract

The current paper presents a two degree of freedom model for the problem of nano/micromirrors under the effect of vdW force. Energy method, the principal of minimum potential energy is employed for finding the equilibrium equations governing the deflection and the rotation of the nano/micromirror. Then using the implicit function theorem, a coupled bending-torsion model is presented for the pull-in characteristics of nano/micromirrors under vdW force and the concept of instability mode is introduced. It is observed that with increasing the ratio of the bending stiffness to the torsion stiffness, the dominant instability mode changes from bending mode to the torsion mode. It is shown that...

#### Application of electrostatically actuated carbon nanotubes in nanofluidic and bio-nanofluidic sensors and actuators

, Article Measurement: Journal of the International Measurement Confederation ; Volume 73 , September , 2015 , Pages 127-136 ; 02632241 (ISSN) ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
Elsevier
2015

Abstract

The paper investigates the effects of fluid flow on the static and dynamic behaviors of electrostatically actuated carbon nanotubes using nonlocal elasticity theory. The influences of various parameters of fluid flow including fluid viscosity, velocity, mass and temperature on the mechanical behaviors of the carbon nanotubes under static and step DC voltages are studied using this theory. The results computed from the nonlocal elasticity theory are compared with those estimated using the classical elasticity theorem and the outcomes demonstrate the applicability of the electrostatically actuated carbon nanotubes as nano sensors and nano actuators in nanofluidic systems. The nanosystem can be...

#### On the pull-in instability of double-walled carbon nanotube-based nano electromechanical systems with cross-linked walls

, Article Fullerenes Nanotubes and Carbon Nanostructures ; Volume 23, Issue 4 , Dec , 2015 , Pages 300-314 ; 1536383X (ISSN) ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
Taylor and Francis Inc
2015

Abstract

This paper presents the deflection and pull-in instability of the double-walled carbon nanotubes with different dimensions and boundary conditions. Molecular dynamic technique is applied to model the desired behaviors of the nano systems. The effects of cross-linking between the carbon walls are investigated on the pull-in charge. In addition, the influences of axial stretching on the pull-in charge and vibrational frequencies of the carbon nanotubes are scrutinized. The effects of electrostatic charge distribution on the vibration amplitude are also reported

#### Designing an intelligent controller for a molecular valve

, Article 2008 Proceedings of the ASME - 2nd International Conference on Integration and Commercialization of Micro and Nanosystems, MicroNano 2008, 3 June 2008 through 5 June 2008, Kowloon ; 2008 , Pages 195-201 ; 0791842940 (ISBN); 9780791842942 (ISBN) ; Alasty, A ; Sharif University of Technology
2008

Abstract

Too much effort has been done for manipulating individual atoms, using nano-manipulators and Scanning Tunneling Microscopes (STM). On the other hand, characterization and manipulation of nano-flows is of great concern. In the current work a molecular valve has been considered, which is made up of six atoms placed on the circumstance of a circle. A fuzzy controller has been designed for controlling the diameter of this molecular valve. The designed fuzzy controller used singleton fuzzifier, Mamdani inference engine, center average defuzzifier and exponential membership functions. A model based on the classical Molecular Dynamics (MD) is used for modeling the nano-system and passing the states...

#### Chaos control in continuous mode of T-AFM systems using nonlinear delayed feedback via sliding mode control

, Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 11 , 2007 , Pages 201-208 ; 079184305X (ISBN) ; Salarieh, H ; Alasty, A ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2007

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...

#### Trajectory following of a micro motion stage based on closedloop fem simulation

, Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 11 , 2007 , Pages 155-158 ; 079184305X (ISBN) ; Mahboobi, S. H ; Pirouzpanah, S ; Esteki, H ; Sarkar, S ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2007

Abstract

Micro motion stages are one of the essential components in field of micro robotics and ultra fine positioning systems. This research presents the optimum design of a 3-DOF micro motion stage and its position control using FEM simulation. This stage to be studied uses a 3 RRR flexure hinge base compliant mechanism driven by three piezoelectric stack actuators to provide micro scale planar motion. First of all parametric modeling of the stage will be fulfilled in ANSYS environment utilizing a commercial piezostack and different types of flexure hinges. Hence the Jacobian matrix will be achieved for each case. The optimum selection of the hinge form will be achieved upon results of the previous...

#### Nanoscale vibrational behavior of single-layered graphene sheets

, Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 11 , 2007 , Pages 229-235 ; 079184305X (ISBN) ; Ahmadian, M. T ; Vafai, A ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2007

Abstract

Molecular structural mechanics approach is implemented to investigate vibrational behavior of single-layered graphene sheets. By using the atomistic modeling, mode shapes and natural frequencies are obtained. Vibration analysis is performed under different chirality and boundary conditions. Numerical results from the finite element technique are applied to develop empirical equations via a statistical multiple nonlinear regression model. With the proposed empirical equations, fundamental frequencies of single-layered graphene sheets under considered boundary conditions can be predicted within 3 percent accuracy. Copyright © 2007 by ASME

#### An intelligent computer method for vibration responses of the spinning multi-layer symmetric nanosystem using multi-physics modeling

, Article Engineering with Computers ; 2021 ; 01770667 (ISSN) ; Baharvand, A ; Tazeddinova, D ; Habibi, M ; Safarpour, H ; Roco Videla, A ; Selmi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021

Abstract

This article is the first attempt to employ deep learning to estimate the frequency performance of the rotating multi-layer nanodisks. The optimum values of the parameters involved in the mechanism of the fully connected neural network are determined through the momentum-based optimizer. The strength of the method applied in this survey comes from the high accuracy besides lower epochs needed to train the multi-layered network. It should be mentioned that the current nanostructure is modeled as a nanodisk on the viscoelastic substrate. Due to rotation, the centrifugal and Coriolis effects are considered. Hamilton’s principle and generalized differential quadrature method (GDQM) are presented...

#### Characterization of static behavior of a nonlinear doubly clamped microbeam under electrostatic actuation and detection

, Article Proceedings of the ASME Design Engineering Technical Conference ; Volume 1 , August , 2013 ; 9780791855843 (ISBN) ; Barari, A ; Mojahedi, M ; Firoozbakhsh, K ; Sharif University of Technology
American Society of Mechanical Engineers
2013

Abstract

In this study, the static deflection and pull-in instability of the doubly clamped microbeam with a mass attached to its midpoint are investigated. Nonlinear electrostatic forces, fringing fields, base rotation and mid-plane stretching of the beam in this model are considered. First, a system of two nonlinear integro-differential equations are expressed in partial derivatives which describe coupled flexural-flexural motion of electrostatically actuated microbeam gyroscopes under rotation. Then static deflection and pull-in instability of the microgyroscopes acted upon by DC voltages in both (direction and sensing) directions are studied. The equations of static motion are reduced by...

#### Application of nonlocal theory in dynamic pull-in analysis of electrostatically actuated micro and nano beams

, Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011, Washington, DC ; Volume 7 , 2011 , Pages 255-261 ; 9780791854846 (ISBN) ; Pasharavesh, A ; Fallah, A ; Sharif University of Technology
2011

Abstract

One of the most important phenomena related to electrically actuated micro and nano electromechanical systems (MEMSNEMS) is dynamic pull-in instability which occurs when the electrical attraction and beam inertia forces are more than elastic restoring force of the beam. According to failure of classical mechanics constitutive equations in prediction of dynamic behavior of small size systems, nonlocal theory is implemented here to analyze the dynamic pull-in behavior. Equation of motion of an electrostatically actuated micro to nano scale doubly clamped beam is rewritten using differential form of nonlocal theory constitutive equation. To analyze the nonlocal effect equation of motion is...

#### Investigation of magnetic field effect on surface and finite-site free energy in one-dimensional Ising model of nanosystems

, Article Phase Transitions ; Volume 84, Issue 7 , Dec , 2011 , Pages 613-623 ; 01411594 (ISSN) ; Abroshan, H ; Akbarzadeh, H ; Parsafar, G ; Fortunelli, A ; Sharif University of Technology
2011

Abstract

We investigate a one-dimensional (1-D) Ising model for finite-site systems. The finite-site free energy and the surface free energy are calculated via the transfer matrix method. We show that, at high magnetic fields, the surface free energy has an asymptotic limit. The absolute surface energy increases when the value of f (the ratio of magnetic field to nearest-neighbor interactions) increases, and for f ≥10 approaches a constant value. For the values of f ≥0.2, the finite-site free energy also increases, but slowly. The thermodynamic limit in which physical properties approach the bulk value is also explored

#### Investigation of size effects on the physical properties of one-dimensional ising models in nanosystems

, Article Molecular Physics ; Volume 109, Issue 3 , Feb , 2011 , Pages 385-395 ; 00268976 (ISSN) ; Daryaei, E ; Parsafar, G ; Fortunelli, A ; Sharif University of Technology
2011

Abstract

Ising models in nanosystems are studied in the presence of a magnetic field. For a one-dimensional (1-D) array of spins interacting via nearest-neighbour and next-nearest-neighbour interactions we calculate the heat capacity, the surface energy, the finite-size free energy and the bulk free energy per site. The heat capacity versus temperature exhibits a common wide peak for systems of any size. A small peak also appears at lower temperatures for small arrays when the ratio of magnetic field spin interaction energy over the nearest-neighbour spin-spin interaction energy, f, is within 0 < F ≤ 0.10 . The peak becomes smaller for longer array and eventually vanishes for long arrays,...