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Free vibration analysis of nanocones using a nonlocal continuum model
, Article Physics Letters, Section A: General, Atomic and Solid State Physics ; Volume 375, Issue 41 , 2011 , Pages 3593-3598 ; 03759601 (ISSN) ; Fotouhi, M. M ; Haddadpour, H ; Sharif University of Technology
2011
Abstract
This Letter aims at the investigation of free-vibration properties of nanocones based on a nonlocal continuum shell model. A novel approach is used for derivation of the governing equations of motion and the Galerkin technique is used to obtain the natural frequencies of vibrations. The effects of small-scale and geometrical parameters of the nanocone on the natural frequencies are studied and some conclusions are drawn
Operation of multi-carrier microgrid (MCMG) considering demand response
, Article Journal of Operation and Automation in Power Engineering ; Volume 7, Issue 1 , 2019 , Pages 119-128 ; 23224576 (ISSN) ; Jadid, S ; Ehsan, M ; Sharif University of Technology
University of Mohaghegh Ardabili, Faculty of Electrical Engineering
2019
Abstract
In this paper, the operation of a future distribution network is discussed under the assumption of a multi-carrier microgrid (MCMG) concept. The new model considers a modern energy management technique in electricity and natural gas networks based on a novel demand side management (DSM) which the energy tariff for responsive loads are correlated to the energy input of the network and changes instantly. The economic operation of MCMG is formulated as an optimization problem. In conventional studies, energy consumption is optimized from the perspective of each infrastructure user without considering the interactions. Here, the interaction of energy system infrastructures is considered in the...
Size-dependent vibrational behavior of a Jeffcott model for micro-rotor systems
, Article Journal of Mechanical Science and Technology ; Volume 30, Issue 1 , 2016 , Pages 35-41 ; 1738494X (ISSN) ; Asghari, M ; Sharif University of Technology
Korean Society of Mechanical Engineers
Abstract
In this study, several analytical expressions are obtained for the vibrational characteristics of a Jeffcott model for micro-rotor systems based on the strain gradient theory to investigate the small-scale effects on the model. The Jeffcott model consists of a massless microrotating shaft and a disk as a rotor with eccentricity. The disk is mounted on the middle of the shaft. Two second-order differential equations associated with the oscillating motion of the rotor in the plane perpendicular to the longitudinal axis are presented and transformed into a complex form. The stiffness of the system is determined by obtaining the deflection of a strain-gradient-based nonrotating microbeam...
Thermoelastic damping in strain gradient microplates according to a generalized theory of thermoelasticity
, Article Journal of Thermal Stresses ; Volume 43, Issue 4 , 2020 , Pages 401-420 ; Asghari, M ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
This paper deals with the small-scale effects on the thermoelastic damping (TED) in microplates. The coupled equations of motion and heat conduction are provided utilizing the strain gradient theory (SGT) and the dual-phase-lag (DPL) heat conduction model. Solving these equations and adopting the Galerkin method, the real and imaginary parts of frequency are extracted. The complex frequency approach is then employed to present a size-dependent expression for evaluating TED in thin plates. An analytical expression for TED incorporating small-scale effects is also derived on the basis of the energy dissipation approach. To survey the effect of different continuum theories on TED, the results...
Small scale effects on the stability of carbon nano-peapods under radial pressure
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 43, Issue 5 , March , 2011 , Pages 1050-1055 ; 13869477 (ISSN) ; Naghdabadi, R ; Rafati Heravi, J ; Sharif University of Technology
2011
Abstract
In this paper, a nonlocal elasticity formulation is presented for analyzing the instability of nano-peapods by modeling the nanotube as a shell. Using the nonlocal elasticity theory, the small scale characteristics of Carbon Nano-Peapods (CNPs) are taken into account. While the classical elastic shell model overestimates the critical pressure for the onset of structural instability of carbon nanotubes, the obtained results show that the nonlocal elastic shell model for nano-peapods can potentially provide better predictions. According to the results, it is concluded that the presence of C 60 inside (10,10) Carbon Nanotubes (CNTs) significantly increases the stability resistance of the single...
On dynamic pull-in instability of electrostatically actuated multilayer nanoresonators: A semi-analytical solution
, Article ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik ; Volume 99, Issue 9 , 2019 ; 00442267 (ISSN) ; Sharif University of Technology
Wiley-VCH Verlag
2019
Abstract
Based on the nonlocal Euler–Bernoulli beam theory, a theoretical approach is developed to investigate the effects of small scale and intermolecular force on the dynamic pull-in behavior of electrostatically actuated nanoresonators. To this purpose, nanoresonators are modeled as multilayer beams with rectangular cross-sections and fixed-fixed and fixed-free end conditions which are embedded in an elastic medium containing Winkler and Pasternak elastic foundations. Also, the effects of nonlocal parameter, fringing field due to the finite width of beams, Casimir or van der Waals intermolecular forces, nonlinear term induced by mid-plane stretching and Winkler and Pasternak elastic foundations...
Design, Construction and Experimental Study of Effect of a Pressure Intensifier Device on a Small Scale Reverse Osmosis System
, M.Sc. Thesis Sharif University of Technology ; Arghavani Hadi, Jamal (Supervisor)
Abstract
Nowadays, water and energy shortage is the main concern of many industries. Every saving that could be done is valuable. In the first step of this project, energy recovery devices that are used in reverse osmosis systems, are reviewed and advantages and disadvantages of each system are investigated. These apparatuses save energy by recovering high-pressure energy from leaving brine and reduce the energy consumption of the device. The main focus of this study is energy consumption of the device that is used for desalination of seawater in reverse osmosis systems and on this basis, different energy recovery devices are compared. According to the investigation, results showed that most of the...
Uncertainty analysis of wind-wave predictions in Lake Michigan
, Article China Ocean Engineering ; Volume 30, Issue 5 , 2016 , Pages 811-820 ; 08905487 (ISSN) ; Ataie Ashtiani, B ; Hamidi, S. A ; Sharif University of Technology
Springer Verlag
Abstract
With all the improvement in wave and hydrodynamics numerical models, the question rises in our mind that how the accuracy of the forcing functions and their input can affect the results. In this paper, a commonly used numerical third-generation wave model, SWAN is applied to predict waves in Lake Michigan. Wind data are analyzed to determine wind variation frequency over Lake Michigan. Wave predictions uncertainty due to wind local effects are compared during a period where wind has a fairly constant speed and direction over the northern and southern basins. The study shows that despite model calibration in Lake Michigan area, the model deficiency arises from ignoring wind effects in small...
Estimating the mixing matrix in underdetermined Sparse Component Analysis (SCA) using consecutive independent component analysis (ICA)
, Article 16th European Signal Processing Conference, EUSIPCO 2008, Lausanne, 25 August 2008 through 29 August 2008 ; 2008 ; 22195491 (ISSN) ; Pad, P ; Babaie Zadeh, M ; Jutten, C ; Sharif University of Technology
2008
Abstract
One of the major problems in underdetermined Sparse Component Analysis (SCA) is the appropriate estimation of the mixing matrix, A, in the linear model x(t) = As(t), especially where more than one source is active at each instant of time (It is called 'multiple dominant problem'). Most of the previous algorithms were restricted to single dominant problem in which it is assumed that at each instant, there is at most one single dominant component. Moreover, because of high computational load, all present methods for multiple dominant problem are practical only for small scale cases (By 'small scale' we mean that the average number of active sources at each instant, k, is less than 5). In this...
A holistic survey on mechatronic Systems in Micro/Nano scale with challenges and applications
, Article Journal of Micro-Bio Robotics ; 2021 ; 21946418 (ISSN) ; Jalili, N ; Ahmadian, M. T ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Micro/Nano mechatronic systems might be defined as systems that include nano- or micro-scale components. These components can be sensors, actuators, and/or physical structures. Furthermore, the high-precision control laws for such small scales are important to ensure stability, accuracy, and precision in these systems. In this writing, four categories of such small-scale systems are considered by providing multifarious novel or key examples from the literature: control engineering and modeling, design and fabrication, measurement engineering, and sensor/actuator development. The applications discussed in the examples vary from nano-positioners, crucial in systems such as atomic force...
Analytical study on size-dependent static pull-in voltage of microcantilevers using the modified couple stress theory
, Article International Journal of Engineering Science ; Volume 54 , May , 2012 , Pages 99-105 ; 00207225 (ISSN) ; Sharif University of Technology
2012
Abstract
In this paper an analytical solution for size-dependent response of cantilever micro-beams is presented. Using the modified couple stress theory, the small scale effects are accounted for. Employing the Modified Variational Iteration Method, efficient and accurate analytical expressions for the deflection of the micro-beam are presented. Very good agreement is observed between the present work results and available experimental data. This study may be helpful to characterize the size-dependent mechanical properties of MEMS. Consequently, the proposed analytical solution can be used as an efficient tool for studying the effects of the material or geometrical parameters on small scale devices...
Flexural vibration characteristics of micro-rotors based on the strain gradient theory
, Article International Journal of Applied Mechanics ; Volume 7, Issue 5 , October , 2015 ; 17588251 (ISSN) ; Hashemi, M ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2015
Abstract
In this paper, the coupled three-dimensional flexural vibration of micro-rotors is investigated by taking into account the small-scale effects utilizing the strain gradient theory, which is a powerful nonclassical continuum theory in capturing small-scale effects. A micro-rotor consists mainly of a flexible micro-rotating shaft and a disk. With the aid of Hamilton's principle, governing equations of motion are derived and then transformed to the complex form. By implementing the Galerkin's method, a coupled ordinary differential equation is attained for the system. Expressions for the first two natural frequencies of the spinning micro-rotors are obtained with truncated two-term equation....
Small-scale building load forecast based on hybrid forecast engine
, Article Neural Processing Letters ; 2017 , Pages 1-23 ; 13704621 (ISSN) ; Talebpour, F ; Safaee, E ; Ghadimi, N ; Abedinia, O ; Sharif University of Technology
Abstract
Electricity load forecasting plays an important role for optimal power system operation. Accordingly, short term load forecast (STLF) is also becoming an important task by researchers to tackle the mentioned problem. As a consequence of the highly non-smooth and volatile trend of the load time series specially in building levels, its STLF is even a more complex procedure than that of a power system. For this purpose, in this paper we proposed a new prediction model based on a new feature selection algorithm and hybrid forecast engine of enhanced version of empirical mode decomposition named sliding window EMD bundled with an intelligent algorithm. The proposed forecast engine is combined...
Small-Scale building load forecast based on hybrid forecast engine
, Article Neural Processing Letters ; Volume 48, Issue 1 , 2018 , Pages 329-351 ; 13704621 (ISSN) ; Talebpour, F ; Safaee, E ; Ghadimi, N ; Abedinia, O ; Sharif University of Technology
Springer New York LLC
2018
Abstract
Electricity load forecasting plays an important role for optimal power system operation. Accordingly, short term load forecast (STLF) is also becoming an important task by researchers to tackle the mentioned problem. As a consequence of the highly non-smooth and volatile trend of the load time series specially in building levels, its STLF is even a more complex procedure than that of a power system. For this purpose, in this paper we proposed a new prediction model based on a new feature selection algorithm and hybrid forecast engine of enhanced version of empirical mode decomposition named sliding window EMD bundled with an intelligent algorithm. The proposed forecast engine is combined...
The second strain gradient functionally graded beam formulation
, Article Composite Structures ; Volume 188 , 15 March , 2018 , Pages 15-24 ; 02638223 (ISSN) ; Asghari, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
A size-dependent formulation for the Euler-Bernoulli nano- and micro-beams made of functionally graded materials (FGMs) is presented. The formulation is developed on the basis of the second strain gradient theory (SSGT). This theory is a powerful non-classical continuum theory capable of capturing the small-scale effects in the mechanical behavior of small-scale structures. To drive the governing equations of motion along with the general form of boundary conditions, the Hamilton principle is utilized. Due to the inhomogeneity through the thickness of functionally graded beams, the two equations which govern the axial and flexural deformations are coupled. In two case studies with different...
Operation of networked multi-carrier microgrid considering demand response
, Article COMPEL - The International Journal for Computation and Mathematics in Electrical and Electronic Engineering ; Volume 38, Issue 2 , 2019 , Pages 724-744 ; 03321649 (ISSN) ; Jadid, S ; Ehsan, M ; Sharif University of Technology
Emerald Group Publishing Ltd
2019
Abstract
Purpose: Microgrids are inclined to use renewable energy resources within the availability limits. In conventional studies, energy interchange among microgrids was not considered because of one-directional power flows. Hence, this paper aims to study the optimal day-ahead energy scheduling of a centralized networked multi-carrier microgrid (NMCMG). The energy scheduling faces new challenges by inclusion of responsive loads, integration of renewable sources (wind and solar) and interaction of multi-carrier microgrids (MCMGs). Design/methodology/approach: The optimization model is formulated as a mixed integer nonlinear programing and is solved using GAMS software. Numerical simulations are...
Effects of couple stresses on the in-plane vibration of micro-rotating disks
, Article JVC/Journal of Vibration and Control ; Volume 26, Issue 13-14 , 2020 , Pages 1246-1259 ; Jahangiri, M ; Asghari, M ; Sharif University of Technology
SAGE Publications Inc
2020
Abstract
Micro-rotating disks are extensively used in micro-electromechanical systems such as micro-gyroscopes and micro-rotors. Because of the sensitivity of these elements, enough knowledge about the mechanical behavior of these structures is an essential matter for designers and fabricators. The small-scale effects on the in-plane free vibration of such micro-disks present an important aspect of the mechanical behavior of these elements. The small-scale effects on the in-plane free vibration of these micro-disks are investigated in this study using the modified couple stress theory. By using the Hamilton principle, the partial differential equations governing the coupled radial and tangential...
Torsional vibration induced by gyroscopic effect in the modified couple stress based micro-rotors
, Article European Journal of Mechanics, A/Solids ; Volume 81 , May–June , 2020 ; Asghari, M ; Bagheri, E ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this research, the small-scale effects in the torsional vibration of the micro-rotors with eccentric micro-disks are investigated based on the modified couple stress theory. The torsional deformation of the micro-shaft described by function φ(x,t) is considered to be independent of the flexural deformation described by functions v(x,t) and w(x,t). Using Hamilton's principle, the system of coupled nonlinear governing partial differential equations of motion and the associated boundary conditions are derived. The system of equations includes one corresponding to the torsional deformation and two others corresponding to the flexural deformation. By employing the Galerkin method, the system...
On size-dependent generalized thermoelasticity of nanobeams
, Article Waves in Random and Complex Media ; 2022 ; 17455030 (ISSN) ; She, C ; Xu, Y.-P ; Esmaeili, S ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
In this article, a size-dependent generalized thermoelasticity model is established to appraise the small-scale effect on thermoelastic vibrations of Euler-Bernoulli nanobeams. Small-scale effect on the structure and heat conduction is captured by exploiting nonlocal strain gradient theory (NSGT) and nonclassical heat conduction model of Guyer and Krumhansl (GK model). NSGT enables the model to account for both nonlocal and strain gradient effects on structure, and GK formulation empowers the model to incorporate both nonlocal and lagging effect into heat conduction equation. The normalized forms of size-dependent equations of motion and heat conduction are provided by introducing some...
Stability Analysis of Hybrid Nanotubes Based on the Nonlocal Continuum Theories
, M.Sc. Thesis Sharif University of Technology ; Asghari, Mohsen (Supervisor)
Abstract
Strong van der Waals (vdW) potential fields of carbon nanotubes (CNTs) makes them capable to encapsulate some nanostructures inside their hollow space, which leads to the construction of new hybrid nanostructures under specific conditions. Carbon nano-peapods, carbon nanowires and the hybrid of DNA and CNT are the main categories of hybrid nanostructures of CNT. Characteristics of hybrid nanotubes are unique and different from those of CNT. In nanostructures, the lattice spacing between individual atoms is considerable with respect to the structural dimensions. Also, the range of internal characteristic length is relatively close to external ones. So that utilizing the classical continuum...