Sharif Digital Repository

The present work develops direct graded boundary integral equation formulation for behavior investigation of the inhomogeneous media made of functionally graded materials. The isoparametric boundary elements, the elastostatic governing equations and a weighted residual technique are implemented with the material characteristics that vary continuously along a given dimension. The resulting algorithm is capable of solving the quasistatic problems for elastic functionally graded media with a variety of the boundary conditions and loadings. The inhomogeneous media is made of a ceramic-metal mixture, in which the material properties vary continuously according to a power law graded distribution... 

The objective of this study is to develop a general finite element formulation associated with an incremental adaptive procedure which established for thermoviscoelastic stress analysis of orthotropic cylinders made of polymers. This paper concerned with development of a numerical algorithm for the solution of the quasistatic initial/boundary value problems involving the linear viscoelastic media with thermal and mechanical deformations. The viscoelastic constitutive equations, represented in an integral form and involving relaxation functions, are transformed into an incremental algebraic relation. An incremental relaxation is then developed for the finite element formulation to deal with... 

In this study, two moving-bed biofilm reactors (MBBR1 and MBBR2) filled with different size of carrier media (Kaldnes K1 and Kaldnes K1 micro, respectively) were subjected to soluble (sugar and sodium acetate (Ac)) substrate and mixture of soluble and particulate (particulate potato starch (PS)) substrate in a very high organic loading rate (12 kgCOD/m3·d) at different temperatures (26 and 15°C, in MBBR1 and MBBR2, respectively). The effects of carrier type and substrate on biofilm structure and reactor performance have been studied. Starch was removed by adsorption at the biofilm surface and hydrolyzed which caused substrate gradient in MBBR1, however, hydrolyzed uniformly within biofilm in... 

Let R be a ring with nonzero identity. The unit graph of R, denoted by G(R), has its set of vertices equal to the set of all elements of R; distinct vertices x and y are adjacent if and only if x + y is a unit of R. In this article, the basic properties of G(R) are investigated and some characterization results regarding connectedness, chromatic index, diameter, girth, and planarity of G(R)are given. (These terms are defined in Definitions and Remarks 4.1, 5.1, 5.3, 5.9, and 5.13.)  

This paper presents the creep behavior of various FRP (GFRP, CFRP, and hybrid) bars in order to investigate the effects of different parameters, including the applied stress levels, bar diameter, and the type of fiber and resin in the creep behavior of FRP bars. The creep strains versus time curves were experimentally obtained for 83 days. Moreover, a statistical study, including analysis of variance (ANOVA) and linear Bayesian regression was conducted to investigate the contribution of the studied parameters. The results showed that in GFRP bars the ratio of ultimate creep strain to the initial elastic strain decreased when the applied stresses on the bars exceeded 30% of their ultimate... 

Nucleation and growth of condensing droplets on horizontal surfaces are investigated via a 2-D double distribution function thermal lattice Boltzmann method. First, condensation on completely uniform surface is investigated and different mechanisms which cause dropwise and filmwise condensation are studied. The results reveal the presence of cooled vapor layer instability in the condensation on completely smooth surfaces. In the second step, condensation on chemically heterogeneous surfaces is investigated. Moreover, the effect of non-uniformity in the surface temperature is also studied. The results indicate that the vapor layer instability and the nucleation start from the heterogeneities.... 

The aim of current research is to investigate the substrate electropolishing effect on corrosion resistance of Ni-Mo thin films. For this purpose, corrosion resistance of coatings deposited on mild steel substrates, that was electropolished or mechanically polished, have been compared in 3.5 wt.% NaCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The structural properties of Ni-Mo thin films were evaluated using X-ray diffraction (XRD) and their morphology, microstructure and chemical composition were also investigated using scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). Temperature and acidity of deposition... 

This study was aimed at gaining an improved understanding of the behavior of glass fiber-reinforced polymer laminates at elevated temperatures by means of testing laminate specimens with unidirectional, woven, and randomly distributed (chopped strand mat) fibers. The testing parameters were temperature, the type of fiber, and the thickness of the laminates. The failure modes of the specimens and their elasticity moduli at ambient temperature were investigated, and analysis of variance was conducted to determine the contribution of each parameter to the behavioral test results. The findings showed that among the parameters, an increase in temperature exerted the strongest effect on the... 

This article presents an investigation on the durability of different glass-fibre-reinforced polymer composites when subjected to harsh outdoor conditions, including freeze/thaw cycles, ultraviolet radiation and moisture, as well as when used with seawater sea-sand concrete for construction applications. To achieve this, the effects of a number of parameters, including the environment of exposure, exposure time, profile cross-sectional configuration and orientation of fibres, on the mechanical properties of different glass-fibre-reinforced polymer composites were studied. To investigate the degradation of the mechanical properties, three-point bending, compression and tension tests were... 

A complete cycle of droplet nucleation, growth, coalescence and jumping on different textured hydrophobic and superhydrophobic surfaces is studied for the first time, using a 2-D double distribution function thermal lattice Boltzmann method. First, droplet nucleation mechanism on smooth and rough surfaces is studied in detail. The results reveal the presence of cooled vapor layer instability in the condensation on completely smooth surfaces. However, on the rough surfaces and near the roughness a completely different mechanism is observed and the nucleation occurs on the roughness wedges. Also, the condensation on different textured surfaces with nominal contact angles θa=90°,120°,155° is... 

In the present study, the hybrid reinforcements (Fe3O4–SiC) novel composite has been successfully fabricated by powder metallurgy method. Adding Fe3O4 nanoparticles and SiC hybrid reinforcements in the aluminium matrix, improved the magnetic permeability of aluminium matrix composites as well as, thermal properties without mechanical degradation. In this study, the aim was to define the influence of SiC–Fe3O4 nanoparticles on microstructural, thermal, electrical, and magnetic properties of the composite. Based on obtained results, the highest density and hardness is 2.72 g/cm3 and 93 HV respectively. Adding (10–30 wt% SiC) into Al–15Fe3O4 slightly improved the magnetic saturation from... 

This article presents an investigation on the durability of different glass-fibre-reinforced polymer composites when subjected to harsh outdoor conditions, including freeze/thaw cycles, ultraviolet radiation and moisture, as well as when used with seawater sea-sand concrete for construction applications. To achieve this, the effects of a number of parameters, including the environment of exposure, exposure time, profile cross-sectional configuration and orientation of fibres, on the mechanical properties of different glass-fibre-reinforced polymer composites were studied. To investigate the degradation of the mechanical properties, three-point bending, compression and tension tests were... 

In this research, the mechanical properties of various glass fibre reinforced polymer (GFRP) pultruded profiles exposed to seawater sea sand concrete (SWSSC) and its combination with UV radiation and water vapour condensation were studied. The effect of different conditions, duration of conditioning, and the profile cross-section configuration on the mechanical properties were investigated. Three-point bending, tension, and compression tests were carried out to obtain the mechanical properties, including flexural, tensile and compressive strengths and tensile elastic modulus. Furthermore, in order to scrutiny the mechanisms and extent of damage, scanning electron microscopy (SEM) was carried... 

Recently, with the growth and development of distributed generation (DGs) and energy storage systems (ESSs), as well as smart control equipment, microgrids (MGs) have been developed. Microgrids are comprised of a limited number of constitutive parts, including loads, DGs, ESSs, and electric vehicles (EVs). This paper presents a novel scheme to manage active and reactive powers, based on DGs, ESSs, and EVs to reduce the total operation cost including power generation and emission costs. Simultaneous management of active and reactive power makes it possible to consider grid operation constraints together. In the proposed schedule, the vehicles are assumed to be plug-in hybrid electric... 

The present research examines the effects of UV radiation, moisture and elevated temperature on the mechanical properties of GFRP pultruded profiles. Flexural, compressive and tensile properties of different GFRP sections were studied after they were exposed for 1000, 1500, 2000 and 3000 h to UV radiation and water vapour condensation cycles. Mechanical tests, including three-point bending, compression and tension tests, SEM analyses, and statistical studies were conducted to gather comprehensive results. The results showed that the mechanical properties of various GFRP sections generally decreased with the duration of conditioning: however, the rate of the decrease that was only slight up...