Sharif Digital Repository

In this study, simple analytical expressions are presented for large amplitude free vibration and post-buckling analysis of functionally graded beams rest on nonlinear elastic foundation subjected to axial force. Euler-Bernoulli assumptions together with Von Karman's strain-displacement relation are employed to derive the governing partial differential equation of motion. Furthermore, the elastic foundation contains shearing layer and cubic nonlinearity. He's variational method is employed to obtain the approximate closed form solution of the nonlinear governing equation. Comparison between results of the present work and those available in literature shows the accuracy of this method. Some... 

HSE management is one of the key topics in project management that plays a significant role in indication of success and soundness of projects. According to the official reports and statistics, construction industry has annually incurred a great deal of expenses and losses due to neglecting the role of HSE issues in the projects worldwide. Since many challenges and problems related to HSE faced Iranian civil engineers and construction managers, recently the HSE have been regarded as a highly critical issue in Iran. Observations show that many Iranian managers and engineers, in their daily activities, have the tendency to ignore the HSE related rules. The aim of this research is to evaluate... 

In this study, nonlinear bending of functionally graded (FG) circular sector plates with simply supported radial edges subjected to transverse mechanical loading has been investigated. Based on the first-order shear deformation plate theory with von Karman strain-displacement relations, the nonlinear equilibrium equations of sector plates are obtained. Introducing a stress function and a potential function, the governing equations which are five non-linear coupled equations with total order of ten are reformulated into three uncoupled ones including one linear edge-zone equation and two nonlinear interior equations with total order of ten. The uncoupling makes it possible to present... 

In this paper, free vibration analysis of thin symmetrically laminated skew plates with fully clamped edges is investigated. The governing differential equation for skew plate which is a fourth order partial differential equation (PDE) is obtained by transforming the differential equation in Cartesian coordinates into skew coordinates. Based on the multi-term extended Kantorovich method (MTEKM) an efficient and accurate approximate closed-form solution is presented for the governing PDE. Application of the MTEKM reduces the governing PDE to a dual set of ordinary differential equations. These sets of equations are then solved with infinite power series solution, in an iterative manner until... 

Free vibration analysis of moderately thick rectangular FG plates on elastic foundation with various combinations of simply supported and clamped boundary conditions are studied. Winkler model is considered to describe the reaction of elastic foundation on the plate. Governing equations of motion are obtained based on the Mindlin plate theory. A semi-analytical solution is presented for the governing equations using the extended Kantorovich method together with infinite power series solution. Results are compared and validated with available results in the literature. Effects of elastic foundation, boundary conditions, material, and geometrical parameters on natural frequencies of the FG... 

Given a division ring D with center F, the structure of maximal subgroups M of GL n(D) is investigated. Suppose D ≠ F or n > 1. It is shown that if M/(M ∩ F*) is locally finite, then char F = p > 0 and either n = 1, [D:F] = p 2 and M ∪ {0} is a maximal subfield of D, or D = F, n = p, and M ∪ {0} is a maximal subfield of M p(F), or D = F and F is locally finite. It is also proved that the same conclusion holds if M/(M ∩ F*) is torsion and D is of finite dimension over F. Furthermore, it is shown that if the r-th derived group M (r) of M is locally finite, then either M (r) is abelian or F is algebraic over its prime subfield  

Given a finite dimensional F-central simple algebra A = Mn(D), the connection between the Frattini subgroup Φ(A*) and Φ(F*) via Z(A′), the center of the derived group of A*, is investigated. Setting G = F* ∩ Φ(A*), it is shown that Φ (F*)Z(A′) ⊂ G ⊂ (∩p F*p) Z(A′) where the intersection is taken over primes p not dividing the degree of A. Furthermore, when F is a local or global field, the group G is completely determined. Using the above connection, Φ(A*) is also calculated for some particular division rings D  

In the proof of Subcase 2 of Theorem 5 in Mahdavi-Hezavehi (2004) [2], not all the required steps are considered properly. Here we shall deal with the remaining step of Subcase 2. Therefore, this completes the proof of the main result that if D is an F-central finite-dimensional division algebra and M is a maximal subgroup of GLn (D), D ≠ F, n > 1, and M / M ∩ F* is torsion, then M is abelian-by-finite. © 2009 Elsevier Inc. All rights reserved  

Let D be a division algebra algebraic over its center F. Given a (Krull) valuation v on F, it is shown that v extends to a valuation on D if and only if for each separable element c∈D′ there exists a valuation w on K: = F(c) extending v on F such that K ∩ D’ ⊂ W*,, where D′ is the derived group of D* and W* is the unit group of the valuation ring W of w. © 2017 Taylor & Francis  

Let D be a division algebra algebraic over its center F. Given a (Krull) valuation v on F, it is shown that v extends to a valuation on D if and only if for each separable element c∈D′ there exists a valuation w on K: = F(c) extending v on F such that (Formula presented.), where D′ is the derived group of D* and W* is the unit group of the valuation ring W of w. © 2017 Taylor & Francis  

Based on the first-order shear deformation and Donnell's shell theory with von Karman non-linearity, one decoupled stability equation for buckling analysis of functionally graded (FG) and multilayered cylindrical shells with transversely isotropic layers subjected to various cases of combined thermo-mechanical loadings is developed. To this end, the equilibrium equations are uncoupled in terms of the transverse deflection, the force function and a new potential function. Using the adjacent equilibrium method, one decoupled stability equation which is an eighth-order differential equation in terms of transverse deflection is obtained and conveniently solved to present analytical expressions... 

Let D be a noncommutative finite dimensional F-central division algebra and M a noncommutative maximal subgroup of GLn(D). It is shown that either M contains a noncyclic free subgroup or M is absolutely irreducible and there exists a unique maximal subfield K of Mn(D) such that K*M, K∕F is Galois with Gal(K∕F)≅M∕K* and Gal(K∕F) is a finite simple group. © 2017 Taylor & Francis  

In this paper, the generalized differential quadrature (GDQ) method is used to study free vibration of moderately thick rectangular plate partially resting on Pasternak foundation. The foundation is considered to support the plate either completely or partially. The governing equations which consist of a system of partial differential equations (PDEs) are obtained based on the first-order shear deformation theory. Various combinations of simply supported, clamped and free boundary conditions are considered. Application of the GDQ method to the governing PDEs resulted in a system of algebraic equations. Solution of this system with accordance to the considered boundary conditions leads to an... 

In this paper, a micromechanical study on rate-dependent behavior of connective tissues is performed. To this end, a hyper viscoelastic constitutive model consisting a hyperelastic part for modeling equilibrium response of tissues and a viscous part using a hereditary integral is proposed to capture the time-dependent behavior of the tissues. With regard to the hierarchical structure of the tissue, strain energy function are developed for modeling elastic response of the tissue constituents i.e. collagen fibers and ground matrix. The rate-dependency is incorporated into the model using a viscous element with rate-dependent relaxation time. The proposed constitutive model is implemented into... 

In this paper, a micromechanical model for connective soft tissues based on the available histological evidences is developed. The proposed model constituents i.e. collagen fibers and ground matrix are considered as hyperelastic materials. The matrix material is assumed to be isotropic Neo-Hookean while the collagen fibers are considered to be transversely isotropic hyperelastic. In order to take into account the effects of tissue structure in lower scales on the macroscopic behavior of tissue, a strain energy density function (SEDF) is developed for collagen fibers based on tissue hierarchical structure. Macroscopic response and properties of tissue are obtained using the numerical... 

In this paper, a constitutive and micromechanical model for prediction of rate-dependent behavior of connective tissues (CTs) is presented. Connective tissues are considered as nonlinear viscoelastic material. The rate-dependent behavior of CTs is incorporated into model using the well-known quasi-linear viscoelasticity (QLV) theory. A planar wavy representative volume element (RVE) is considered based on the tissue microstructure histological evidences. The presented model parameters are identified based on the available experiments in the literature. The presented constitutive model introduced to ABAQUS by means of UMAT subroutine. Results show that, monotonic uniaxial test predictions of... 

Drop formation in cross-junction micro-channels is numerically studied using the lattice Boltzmann method with pseudo-potential model. To verify the simulation, the results are compared to previous numerical and experimental data. Furthermore, the effects of capillary number, flow rate ratio, contact angle, and viscosity ratio on the flow patterns, drop length, and interval between drops are investigated and highlighted. The results show that the drop forming process has different regimes, namely, jetting, drop, and squeezing regimes. Also, it is shown that increasing in the flow rate ratio in the squeezing regime causes increment in drop length and decrement in drops interval distance. On... 

In this article, a three-dimensional numerical investigation is performed to study the effect of a magnetic field on a ferrofluid inside a tube. This study comprehensively analyzes the influence of a non-uniform magnetic field in the heat transfer of a tube while a ferrofluid (water with 0.86 vol% nanoparticles (Fe3O4) is let flow. The SIMPLEC algorithm is used for obtaining the flow and heat transfer inside the tube. The influence of various parameters, such as concentration of nanoparticles, intensity of the magnetic field, wire distance and Reynolds number, on the heat transfer is investigated. According to the obtained results, the presence of a non-uniform magnetic field significantly... 

In the present work, micro-climate control of a fan-ventilated tunnel greenhouse with evaporative cooling is investigated via simulation study. For this purpose, the adaptive generalized predictive control (AGPC) strategy is adopted to control temperature, relative humidity, and CO2 concentration in the greenhouse on extremely hot summer days. A dynamic model which integrates a distributed model of greenhouse micro-climate with a crop growth model is used for numerical simulation of the tunnel greenhouse. The controller performance is analyzed via numerical simulation. The relative gain array analysis confirms that greenhouse micro-climatic parameters are highly interactive. However,... 

In this paper, based on the high-order theory (HOT) of sandwich structures, the response of sandwich cylindrical shells with flexible core and any sort of boundary conditions under a general distributed static loading is investigated. The faces and the core are made of isotropic materials. The faces are modeled as thin cylindrical shells obeying the Kirchhoff–Love assumptions. For the core material, it is assumed to be thick and the in-plane stresses are negligible. The governing equations are derived using the principle of the stationary potential energy. Using harmonic differential quadrature method (HDQM), the equations are solved for deformation components. The obtained results are...