Sharif Digital Repository

The vibration of a simply-supported beam with rotary springs at either ends is studied. The governing equations of motion are investigated considering the nonlinear effect of stretching. These equations are made non-dimensional and solved to the first-order approximation using the two known methods, namely, the multiple scales and the mode summation. The first five natural frequencies of the beam for different pairs of the boundary condition parameters are evaluated. A multilayer feed-forward back-propagation artificial neural network is trained using these natural frequencies. The artificial neural network used in this study shows high degree of accuracy for the natural frequency of the... 

The vibration of a simply supported beam with rotary springs at either ends is studied. The governing equations of motion are investigated considering the nonlinear effect of stretching. These equations are made non-dimensional and then solved to first order approximation using the two methods of the multiple scales and the mode summation. The first five natural frequencies of the beam for few pairs of the boundary condition parameters are evaluated. A multilayer feed-forward back-propagation artificial neural network is trained using these natural frequencies. The artificial neural network used in this study shows high degree of accuracy for the natural frequency of the beam with general... 

Combination of three-dimensional (3D) IC technology and network on chip (NoC) is an effective solution to increase system scalability and also alleviate the interconnect problem in large-scale integrated circuits. However, because of the increased power density in 3D NoC systems and the destructive effect of high temperatures on chip reliability, applying thermal management solutions becomes crucial in such circuits. In this study, the authors propose a runtime distributed migration algorithm based on game theory to balance the heat dissipation among processing elements (PEs) in a 3D NoC chip multiprocessor. The objective of this algorithm is to minimise the 3D NoC system's peak temperature,... 

Combination of three-dimensional (3D) IC technology and network on chip (NoC) is an effective solution to increase system scalability and also alleviate the interconnect problem in large-scale integrated circuits. However, because of the increased power density in 3D NoC systems and the destructive effect of high temperatures on chip reliability, applying thermal management solutions becomes crucial in such circuits. In this study, the authors propose a runtime distributed migration algorithm based on game theory to balance the heat dissipation among processing elements (PEs) in a 3D NoC chip multiprocessor. The objective of this algorithm is to minimise the 3D NoC system's peak temperature,... 

Polycarboxylate superplasticizers based on acrylic acid (AA) and maleic anhydride (MAn) were synthesized via free-radical copolymerization with an ethylene glycol monomer and characterized. The copolymerization temperature (ranging from 50 to 90 °C) appeared to be the key operating factor governing the chemical structure of the superplasticizers. The chemical structures of the products were analyzed by gel permeation chromatography, whereas an optimized sample was further analyzed by Fourier transform infrared spectroscopy and 1H-NMR. Superplasticizers of the AA and MAn classes were then incorporated into concrete, and their performances were measured by slump and slump loss tests, where a... 

Asphaltenes are the heaviest and most polar components of crude oils which are commonly stable in the oil, and can precipitate, aggregate and eventually deposit in reservoirs, flow lines, separators, and other systems along production lines due to changes in conditions such as temperature, pressure and composition. There are a few studies published in the literature focusing on the prediction of asphaltene deposition in pipelines, which reveals that there is lack of a comprehensive deposition simulator which fully considers all effective process during asphaltene deposition phenomena. In this work, a novel framework with considering all effective process in asphaltene deposition was... 

An investigation into the dynamics of vehicle-passenger-structure-induced vibration of suspension bridges traversed by accelerating vehicles is carried out. The vehicle including the driver and passengers is modeled as a half-car planer model with six degrees-of-freedom. In addition, the stiffness of compliant bushings at the connecting points of the shock absorbers to the body is considered. The bridge is assumed to obey the Timoshenko beam theory with axial load and arbitrary conventional boundary conditions. The roughness of the bridge is assumed as a differentiable function of location. Due to continuously moving the location of the variable loads on the bridge, and in the presence of... 

In this paper, an analysis is presented of some bronze vessels from recent excavations at the first millennium BC site of Sangtarashan in eastern Luristan, Iran, according to metallography (OM), ICP-OES and SEM-EDS methods to identify alloying as well as manufacturing processes. This study provides new evidence for a better understanding of the bronze archaeometallurgy during the Iron Age in Iran. It concludes that the artifacts contain homogenous and single phase tin bronze (Cu-Sn) alloy. The Sn content in the artifacts also allowed to apply mechanical operations on the vessels without causing brittleness. Apart from tin, other elements that are classified as trace elements were present,... 

The multi-vehicle travelling purchaser problem with priority in purchasing (MTPP-PIP) is a new variant of the classic travelling purchaser problem (TPP) in which the set of products is divided into different priority groups. The purpose of this article is to find the least cost cycles in which each product should be purchased according to its predefined priority. To fit the model with the real world further, multiple purchasers (multi-vehicle) and uncertainty in the products demands are assumed. In this paper, a mathematical programming formulation is developed based on a clustered supplier graph whereby the suppliers are categorised into different clusters according to their corresponding... 

Electrochemical activity of TiO2 nanotube arrays (NTAs) is restricted by a wide band gap of TiO2. To overcome this restriction, we considered systematic research on two effective methods of doping of TiO2 NTAs such as the N-doping and electrochemical reductive doping and predicting the proper application of them. Band gap narrowing was occurred from 3.16 eV for undoped TiO2 NTAs to 2.9 and 2.7 eV at N-doped and self-doped TiO2 ones respectively. The electrochemical responses of the TiO2 NTAs before and after doping were examined by cyclic Voltammetry (CV) curve. To understand the electrochemical behavior of the undoped and doped TiO2 NTAs, electrochemical impedance spectroscopy (EIS) was... 

Although morphological disorder of nanotube structure is further down than the nanoparticular electrode, its density of traps are the hindering effects in the charge transport. In this study, crack-free TiO2 nanotube membranes, which obtained through a re-anodizing process, are fixed on transparent fluorine–tin-oxide glass by applying a few drops of Titanium Isopropoxide without needing the TiO2 powder paste. Front-side illuminated dye sensitized solar cells fabricated by undoped, N-doped and blue TiO2 nanotube membranes are investigated. The electrical characteristics of TiO2 nanotube based dye sensitized solar cells are followed by theoretical analysis using simple one-diode model.... 

HVOF-sprayed coatings (WC-17%Co) and hard chromium coatings corrosion resistances have been compared through electrochemical polarization test in 3.5% NaCl solution. WC-17%Co alloy coatings were deposited on mild steel substrates by High Velocity Oxy-Fuel (HVOF) spray process. The layers of standard and crack free hard chromium coatings were prepared by using Direct Current (DC) and Pulse Current (PC) electroplating process on the mild steel substrates. Hard chromium coatings was characterized as a reference material, to verify whether HVOF-sprayed coatings are suitable as a hard chromium coatings replacement. The microstructure of the coatings was examined by OM, SEM and XRD. Standard hard... 

2-Thenoyltrifluoroacetone has been offered as a mobile carrier in organic phase for the transport and selective separation of yttrium from aqueous media using a liquid membrane system. Perceivably, the use of n-propylamine (PA) in the source phase enhances the transport of yttrium ions. The extraction and stripping conditions have entirely been evaluated and explained. The suggested method has been utilized for the separation of yttrium(III) from its binary mixtures with strontium(II) and some other cations such as Ni2+, Co2+, Ag+, Fe2+, Al3+, Cu2+, Hg2+and Cs+ in aqueous solutions of pH 5.4 in the presence of PA, while 1 M nitric acid was acting as a stripping agent in the receiving... 

Reduction of air pollutants formation from hydrocarbon combustion process requires improvements in combustion systems. The moderate and intense low oxygen dilution (MILD) combustion technique is an opportunity to achieve such a goal. MILD combustion is a combustion regime which can be attained by high temperature preheating and high level dilution. In this paper, the mechanism of CO and CO2 formation for a CH4/H2 fuel mixture is studied under MILD combustion condition of a jet in hot coflow (JHC) burner. This investigation is done using the computational fluid dynamics (CFD) and also zero dimensional well-stirred reactor (WSR) analysis. The RANS equations with modified k-ε equations are... 

The purpose of this research is to investigate the response of concrete-filled composite tube column under concentric and eccentric loads. To evaluate the influence of PVC pipe on the behavior of concrete-filled composite tubes, concrete-filled PVC pipe (CFPT) were modeled by ABAQUS software. The results demonstrate that the presence of the PVC pipe makes the concrete column more ductile and have a significant effect on the stress–strain curve of the CFPT after the peak strength, in a way that the confinement increased by raising the thickness of PVC pipe, but the confinement effect of the PVC pipe decreased by the increment of the column diameter and compressive strength of the concrete... 

The purpose of this research is to investigate the response of concrete-filled composite tube column under concentric and eccentric loads. To evaluate the influence of PVC pipe on the behavior of concrete-filled composite tubes, concrete-filled PVC pipe (CFPT) were modeled by ABAQUS software. The results demonstrate that the presence of the PVC pipe makes the concrete column more ductile and have a significant effect on the stress–strain curve of the CFPT after the peak strength, in a way that the confinement increased by raising the thickness of PVC pipe, but the confinement effect of the PVC pipe decreased by the increment of the column diameter and compressive strength of the concrete... 

AIDS causes increasing mortality every year. With advancements in nanomedicine, different nanomaterials (NMs) have been applied to treat AIDS and overcome its limitations. Among different NMs, nanoparticles (NPs) can act as nanocarriers due to their enhanced solubility, sustained release, targeting abilities and facilitation of drug-dose reductions. This review discusses recent advancements in therapeutics for AIDS/HIV using various NMs, mainly focused on three classifications: polymeric, liposomal and inorganic NMs. Polymeric dendrimers, polyethylenimine-NPs, poly(lactic-co-glycolic acid)-NPs, chitosan and the use of liposomal-based delivery systems and inorganic NPs, including gold and... 

Microburst wind shear is a potential hazard for aviation safety, especially in some crucial phases of flight like take-off and landing. Optimal trajectories could be useful for suitable retrieval of transport aircrafts encountering microburst. These types of trajectories are investigated in this paper for landing phase in two scenarios of escape and landing utilizing the most recent realistic analytical model of the microburst. In this regard, a set of complete six degrees of freedom aircraft's equations of motion is taken in a variation formulation of this problem. This approach is particularly useful for determination of optimal escape or approach trajectories constrained with respect to...