• Steel and Composite Structures
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• v.18 no.6
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• pp.1541-1555
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• 2015

In this paper mechanical behavior of the functional gradient materials (FGM) micro-gripper under thermal load and DC voltage is numerically investigated taking into account the effect of intermolecular forces. In contrary to the similar previous works, which have been conducted for homogenous material, here, the FGM material has been implemented. It is assumed that the FGM micro-gripper is made of metal and ceramic and that material properties are changed continuously along the beam thickness according to a given function. The nonlinear governing equations of the static and dynamic deflection of microbeams have been derived using the coupled stress theory. The equations have been solved using the Galerkin based step-by-step linearization method (SSLM). The solution procedure has been evaluated against available data of literature showing good agreement. A parametric study has been conducted, focusing on the combined effects of important parameters included DC voltage, temperature variation, geometrical dimensions and ceramic volume concentration on the dynamic response and stability of the FGM micro-gripper.

• Advances in Energy Research
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• v.5 no.2
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• pp.129-145
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• 2017

In this study, the use of a micro gas turbine system using biogas to supply heating, cooling and electricity loads of a rural building located in rural area around Tehran has been studied. Initially, the amount of energy needed by the farmhouse was calculated and then the number of needed microturbines was determined. Accordingly, the amount of substances entering biogas digester as well as tank volume were determined. The results of this study showed that village house loads including electrical, heating and cooling and hot water loads can be supplied by using a microturbine with a nominal power of 30 kW and $33.5m^3/day$ of biogas. Digester tank and reservoir tank volumes are $67m^3$ and $31.2m^3$, respectively. The cost of electricity produced by this system is 0.446 US$/kWh. For rural area in Iran, this system is not compatible with micro gas turbine and IC engine system use urban natural gas due to low price of natural gas in Iran, but it can be compatible by wind turbine, photovoltaic and hybrid system (wind turbine& photovoltaic) systems.

• Wind and Structures
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• v.26 no.1
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• pp.1-9
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• 2018

This research studies the dynamic analysis of a concrete column reinforced with titanium dioxide ($TiO_2$) nanoparticles under earthquake load. The effect of nanoparticles accumulation in a region of concrete column is examined using Mori-Tanaka model. The structure is simulated mathematically based on the theory of sinusoidal shear deformation theory (SSDT). By calculating strain-displacement and stress-strain relations, the system energies include potential energy, kinetic energy, and external works are derived. Then, using the Hamilton's principle, the governing equations for the structure are extracted. Using these equations, the response of the concrete column under earthquake load is investigated using the numerical methods of differential quadrature (DQ) and Newark. The purpose of this study is to study the effects of percentage of nanoparticles, nanoparticles agglomeration, geometric parameters and boundary conditions on the dynamic response of the structure. The results indicate that by increasing the volume percent of $TiO_2$ nanoparticles, the maximum dynamic deflection of the structure decreases.

• Structural Engineering and Mechanics
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• v.68 no.3
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• pp.359-368
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• 2018

This paper deals with the dynamic stability of nanocomposite pipes conveying pulsating ferrofluid. The pipe is reinforced by carbon nanotubes (CNTs) where the agglomeration of CNTs are considered based on Mori-Tanaka model. Due to the existence of CNTs and ferrofluid flow, the structure and fluid are subjected to axial magnetic field. Based on Navier-Stokes equation and considering the body forced induced by magnetic field, the external force of fluid to the pipe is derived. For mathematical modeling of the pipe, the first order shear deformation theory (FSDT) is used where the energy method and Hamilton's principle are used for obtaining the motion equations. Using harmonic differential quadrature method (HDQM) and Bolotin's method, the motion equations are solved for calculating the excitation frequency and dynamic instability region (DIR) of the structure. The influences of different parameters such as volume fraction and agglomeration of CNTs, magnetic field, structural damping, viscoelastic medium, fluid velocity and boundary conditions are shown on the DIR of the structure. Results show that with considering agglomeration of CNTs, the DIR shifts to the lower excitation frequencies. In addition, the DIR of the structure will be happened at higher excitation frequencies with increasing the magnetic field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.191-201
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• 2010

This paper presents a new global optimization algorithm based on the branch-and-bound principle using Bspline approximation techniques. It describes the algorithmic components and details on their implementation. The key components include the subdivision of a design space into mutually disjoint subspaces and the bound calculation of the subspaces, which are all established by a real-valued B-spline volume model. The proposed approach was demonstrated with various test problems to reveal computational performances such as the solution accuracy, number of function evaluations, running time, memory usage, and algorithm convergence. The results showed that the proposed algorithm is complete without using heuristics and has a good possibility for application in large-scale NP-hard optimization.

• Steel and Composite Structures
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• v.37 no.1
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• pp.99-115
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• 2020

This article deals with the dynamic analysis in pad concrete foundation containing Silica nanoparticles (SiO₂) subject to seismic load. In order to control the foundation smartly, a piezoelectric layer covered the foundation. The weight of the building by a column on the foundation is assumed with an external force in the middle of the structure. The foundation is located in soil medium which is modeled by spring elements. The Mori-Tanaka law is utilized for calculating the equivalent mechanical characteristics of the concrete foundation. The Kevin-Voigt model is adopted to take into account the structural damping. The concrete structure is modeled by a thick plate and the governing equations are deduced using Hamilton's principle under the assumption of higher-order shear deformation theory (HSDT). The differential quadrature method (DQM) and the Newmark method are applied to obtain the seismic response. The effects of the applied voltage to the smart layer, agglomeration and volume percent of SiO₂ nanoparticles, damping of the structure, geometrical parameters and soil medium of the structure are assessed on the dynamic response. It has been demonstrated by the numerical results that by applying a negative voltage, the dynamic deflection is reduced significantly. Moreover, silica nanoparticles reduce the dynamic deflection of the concrete foundation.

• Korean Journal of Veterinary Research
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• v.35 no.3
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• pp.595-601
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• 1995

Hemodynamic values were assessed in the cows diseased with mastitis. Hemodynamic testes were performed for white blood cell(WBC), red blood cell(RBC), packed cell volume(PCV), hemoglobin concentration, monocyte, eosinophil, neutrophil, lymphocyte, prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen, platelet concentrations, antithrombin-III and plasminogen activities. Significant alterations were observed in the mean values of most analytes. The numbers of monocytes, eosinophil, and neutrophil, and prothrombin time were increased while the number of lymphocyte, activated partial thromboplastin time, thrombin time, fibrinogen concentration, plasminogen activity and platelet concentration were decreased. The number of RBC, PCV, hemoglobin and antithrombin-III activity were unchanged compared with normal mean values. These data indicated that activation of hemodynamic mechanisms was initiated either directly by the endotoxin-releasing or indirectly by the inflammatory mediators released by response to etiologic agents. We suspected that the changes of hemodynamic values in the cows diseased with mastitis were very similar to those of experimental endotoxin-induced mastitis.

• Earthquakes and Structures
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• v.13 no.6
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• pp.589-598
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• 2017

In this paper, dynamic response of the horizontal concrete beam subjected to seismic ground excitation is investigated. The structure is reinforced by $Fe_2O_3$ nanoparticles which have the magnetic properties. The hyperbolic shear deformation beam theory (HSDBT) is used for mathematical modeling of the structure. Based on the Mori-Tanaka model, the effective material properties of concrete beam is calculated considering the agglomeration of $Fe_2O_3$ nanoparticles. Applying energy method and Hamilton's principle, the motion equations are derived. Harmonic differential quadrature method (HDQM) along with Newmark method is utilized for numerical solution of the motion equations. The effects of different parameters such as volume fraction and agglomeration of $Fe_2O_3$ nanoparticles, magnetic field, boundary conditions and geometrical parameters of concrete beam are studied on the dynamic response of the structure. In order to validation of this work, an exact solution is used for comparing the numerical and analytical results. The results indicated that applying magnetic field decreases the of the structure up to 54 percent. In addition, increase too much the magnetic field (Hx>5e8 A/m) does not considerable effect on the reduction of the maximum dynamic displacement.

• Steel and Composite Structures
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• v.32 no.2
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• pp.239-252
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• 2019

Since conical sandwich shells are important structures in the modern industries, in this paper, for the first time, vibration behavior of the truncated conical sandwich shells which include temperature dependent porous FG face sheets and temperature dependent homogeneous core in various thermal conditions are investigated. A high order theory of sandwich shells which modified by considering the flexibility of the core and nonlinear von Karman strains are utilized. Power law rule which modified by considering the two types of porosity volume fractions are applied to model the functionally graded materials. By utilizing the Hamilton's energy principle, and considering the in-plane and thermal stresses in the face-sheets and the core, the governing equations are obtained. A Galerkin procedure is used to solve the equations in a simply supported boundary condition. Uniform, linear and nonlinear temperature distributions are used to model the effect of the temperature changing in the sandwich shell. To verify the results of this study, they are compared with FEM results obtained by Abaqus software and for special cases with the results in literatures. Eigen frequencies variations are surveyed versus the temperature changing, geometrical effects, porosity, and some others in the numerical examples.

• Advances in nano research
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• v.10 no.4
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• pp.385-395
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• 2021

This research concentrates on the effects of distributions and volume fractions of carbon nanotubes (CNT) on the nonlinear bending behavior of deep cylindrical panels reinforced by functionally graded carbon nanotubes under thermo-mechanical loading, hitherto not reported in the literature. Assuming the effects of shear deformation and moderately high value of the radius-to-side ratio (R/a), based on the first-order shear deformation theory (FSDT) and von Karman type of geometric nonlinearity, the governing system of equations is obtained. The analytical solution of field equations is carried out using the Ritz method together with the Newton-Raphson iterative scheme. The effects of radius-to-side ratio, temperature change, and boundary conditions on the nonlinear response of the functionally graded carbon nanotubes reinforced composite deep cylindrical panel (FG-CNTRC) are investigated. It is concluded that, among the five possible distribution patterns of CNT, FG-V CNTRC deep cylindrical panel is strongest with the highest bending moment and followed by UD, X, O, and Ʌ-ones. Also, considering the present deep cylindrical panel formulation increases the accuracy of the results. Hence, according to the noticeable amount of R/a in FG-CNTRC cylindrical panels, it is mandatory to apply strain-displacement relations of deep cylindrical panels for bending analysis of FG-CNTRC which certainly is desirable for industrial application.