Sharif Digital Repository

Motivated by surface plasmon polariton waveguides in the optical regime, spoof surface plasmon (SSP) waveguides have received a lot of attention in terahertz and millimeter wave frequencies.Most research on these kinds of waveguides is numerical. However, some limited analytical work can be seen in the literature. In this paper, one type of SSP waveguide that is composed of a rectangular corrugation with finite lateral width on the ground is considered, and an analytical method, which is inspired byMarcatili's method, is proposed in order to calculate the dispersion curve of the first mode. The results of this analytical method and a numerical commercial eigenmode solver are compared. The... 

This paper analyzes the second-order mode of the spoof surface plasmon (SSP) waveguide, which consists of PEC pillars (dominos) with finite lateral widths on a PEC ground. The space is first divided into four regions. The electromagnetic fields of each region are then written as TE and TM. The boundary conditions and matching integrals are employed to determine the dispersion relations of the second-order mode of the SSP waveguide consisting of two relations. Inspired by Marcatili's method, the analytical approach is to develop a recently-used method for the first mode of the SSP waveguide. The dispersion relations are then solved; therefore, the dispersion curve is plotted. The analytical... 

Indoor communication systems operating at millimeter wave frequencies are getting increasing attention due to their ability of having wider bandwidth and as a result conveying information at higher bit rates. At these systems, the capacity of channel is very important especially where there is no line of sight due to an obstacle. Here we examine the use of a multiple-input multiple-output (MIMO) system in a 2D room with an obstacle at 60 GHz. We estimate the channel by using the closed-form Green's function of the room and show the ability of MIMO to increase the available capacity of the system in the room chiefly behind the obstacle. © 2016 IEEE  

In this study the ability of artificial neural network (ANN) in forecasting the daily NASDAQ stock exchange rate was investigated. Several feed forward ANNs that were trained by the back propagation algorithm have been assessed. The methodology used in this study considered the short-term historical stock prices as well as the day of week as inputs. Daily stock exchange rates of NASDAQ from January 28, 2015 to 18 June, 2015 are used to develop a robust model. First 70 days (January 28 to March 7) are selected as training dataset and the last 29 days are used for testing the model prediction ability. Networks for NASDAQ index prediction for two type of input dataset (four prior days and nine... 

Systematic management of enterprise knowledge, e.g. new ideas, innovations and patents, has a great impact on business sustainability and growth. Without comprehensive assessment of knowledge assets, agile companies can not design and run knowledge promotion programs required for survival in competitive environments in modern economy. A comprehensive framework for the assessment of as-is situation and development of knowledge promotion plans includes (a) assessing the as-is situation- the quantity and quality of organizational knowledge; (b) developing a situational program based on assessment results, business strategy and knowledge maturity indicators; (c) and working out an action plan in... 

In this article, the propagation of one-dimensional stress waves in a plate made of functionally graded materials excited by a harmonic force is studied. The material properties of the functionally graded material plate are assumed to be graded in the thickness direction according to a power law distribution in terms of the volume fractions of the constituents. The governing equations are based on stress-strain relation and the equation of motion. Keeping generality, the functionally graded material plate is assumed as a multilayer with linear material property in each layer while arbitrary exponential material property through the thickness. A plate made of aluminum and alumina is... 

Deformation modeling of an infinite plate of functionally graded materials (FGMs) loaded by normal force to the plate surface is studied. The material properties of FGM plate are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The governing equations are based on stress-strain relation and the equilibrium force equation. Keeping generality, FGM plate has been assumed as a multilayer with linear material property in each layer while arbitrary exponential material property through the thickness. A plate made of Aluminum and Alumina is considered as an example to illustrate the effects of the... 

The aim of this study is to develop a non-linear robust controller with adaptive gains in order to prevent malaria epidemic as a positive system with an uncertain model. The malaria outbreak is modelled by seven non-linear coupled differential equations for the population variables: susceptible, exposed, symptomatic infected and recovered humans and the susceptible, exposed and infected mosquitoes. The non-linear robust adaptive integral-sliding-mode controller is developed in order to appropriately adjust the use of treated bednets, treatment rate of infected individuals and the use of insecticide spray to control malaria epidemic. Accordingly, the numbers of exposed and infected humans and... 

The present article describes the synthesis of a new magnetic polyacrylonitrile-based Pd catalyst involving polyacrylonitrile modified via 2-aminopyridine as an efficient support to immobilize Pd nanoparticles. The simple reusability, easy separation and high stability of this Pd complex make it an excellent candidate to generate a C–O bond via Ph-X activation which is a really important subject in achieving biologically active compounds. It is worth to note access to good and high yields as well as broad substrate scope have resulted from superior reactivity of this catalyst complex. Furthermore, the structure of the magnetic polyacrylonitrile-based heterogeneous catalyst was characterized... 

Aryl benzylsulfonates undergo so-called pseudo-thia-Fries rearrangement under microwave irradiation. Benzylated phenolic compounds have been obtained with the loss of 'SO2' from the starting materials  

Accumulative roll bonding is a severe plastic deformation process used for Cu-Al-Mn shape memory alloy. The main purpose of this study is to investigate the possibility of grain refinement of Cu-9.5Al-8.2Mn (in wt.%) shape memory alloy using accumulative roll bonding and post-deformation annealing. The alloy was successfully subjected to 5 passes of accumulative roll bonding at 600 °C. The microstructure, properties as well as post-deformation annealing of this alloy were investigated by optical microscopy, scanning electron microscopy, x-ray diffraction, differential scanning calorimeter, and bend and tensile testing. The results showed that after 5 passes of ARB at 600 °C, specimens... 

A rapid Michael addition of secondary amines to α,β-unsaturated carbonyl compounds has been achieved in good to excellent yields in the presence of water under microwave irradiation. In the absence of water and under conventional method the reaction does not proceed or take place in very low yield after a long reaction time  

We present a novel pincer ligand based on the pyridine scaffold for functionalizing magnetic GO (graphene oxide). Pincer ligands are known for their great control of coordination spheres in catalysts. GO is used as solid support for immobilizing gold nanoparticles to synthesize a heterogeneous catalyst for reducing nitroarenes. The reduction of nitroarenes to aromatic amines is not only of environmental importance but can be used as a model reaction too. The yields of the reduction reactions are promising. Additionally, the reaction conditions are mild and the catalyst has good recyclability and great stability. The nanocatalyst was monitored and characterized by spectroscopic methods. ©... 

Flight dynamics of the guided vehicle is modelled by the aid of linear and angular equations of motions using Lagrange's approach in this paper. Governing equations of the control system and the elastic behavior of the vehicle are added to the equations of dynamic states. Flexibility effect is modelled using the normal modes, generalized coordinates and forces. For validation of modified FORTRAN simulation code, the stability of specific vehicles is determined and compared with the same results in the literature. Using this code and by solving the governing equations for the desired flight vehicle, the aeroservoelasticity is analyzed and then the results are compared with the rigid cases and... 

Pyrolysis is a commonly used method for the recovery of used lubricating oil (ULO), which should be kinetically improved by a catalyst, due to its high level of energy consumption. In this research, the catalytic effects of carbon nanotube (CNT) and graphene nanoplatelets on the pyrolysis of ULO were studied through thermogravimetric analysis. First, the kinetic parameters of ULO pyrolysis including activation energy were calculated to be 170.12 and 167.01 kJ mol−1 by FWO and KAS methods, respectively. Then, the catalytic effects of CNT and graphene nanoplatelets on pyrolysis kinetics were studied. While CNT had a negligible effect on the pyrolysis process, graphene nanoplatelets... 

An efficient synthesis of polysubstituted thiophene derivatives is achieved via the multicomponent reaction of β-ketodithioesters, α-haloketones, and cyclohexylisocyanide in aqueous medium  

This article presents a failure analysis on a gasoline engine cylinder head made of aluminum alloy, which has been used in passenger cars. During an endurance test, a crack initiated from the interior wall of a hole in the center of the cylinder head and then propagated through the thickness of the cylinder head. The metallurgical examinations are conducted in the crack origin zone. The results show that there are many casting pores due to poor quality of casting in the failed cylinder head which has certainly played a crucial role in initiating the crack. Finite element analysis of the cylinder head is performed to identify the stress components. Modeling of a bolt for the hole shows that... 

In the present study, metal complexes of 1-amidino-O-alkylureas were designed, synthesized and characterized by elemental analyses, FT-IR spectra, XRD, Mass analyses and scanning electron microscopy (SEM). All synthesized complexes were screen as α-Glucosidase inhibitors. According to the in vitro results, the Cu (II) complexes showed superior potency compared to other tested metal complexes. Particularly, [Cu(L-Me)2](Cl)2 (1b) showed the strongest inhibition against α-Glucosidase with an IC50 value of 2.75 ± 0.3 µM which was comparable to that of acarbose (IC50 = 750 µM). These findings are supported by the ligands and enzyme interactions through molecular docking. © 2021 Elsevier B.V  

In this paper, we report that a known dinuclear Fe complex, [tpa(H2O)FeOFe(H2O)tpa](ClO4)4 (tpa: tris(2-pyridylmethyl)amine), is an efficient catalyst toward organic sulfide oxidation in the presence of urea-hydrogen peroxide