Sharif Digital Repository

Developing a simple, cost effective and accurate detection method for L-lysine (Lys), L-leucine (Leu) and glycine (Gly) as the important analytes in clinical diagnostics, biological processes and food industries is of great significance. Herein, we prepared spin-coated TEMPO-oxidized cellulose nanofibrils (TOCNFs) on Quartz Crystal Microbalance (QCM) chip to achieve QCM biodetectors. The coated QCMs were carefully characterized before and after interaction with amino acids (AA) using water contact angle (WCA), Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), Raman spectroscopy, and scanning electron microscopy (SEM). In addition, to study the response of... 

In this study, the fatigue behavior of composite reinforced cracked aluminum 1050 plates is investigated experimentally and numerically. The tests are conducted in four different stress ratios between 0 and 1. At first step, plates with similar cracks and geometries have been prepared. Then the glass/epoxy patches have been attached to the cracked plates using Araldite 2015 adhesive. Fatigue load has been applied to three cases of samples including non-patch, one-side patch and two-side patch, where in all stress ratios the maximum force is considered constant. A three-dimensional finite element analysis is developed in ABAQUS. A good correlation between finite element results and the... 

Background and Objectives: Depression is one of the most prevalent mental disorders among students associated with a major decline in academic and social performance. This study was carried out to determine the prevalence of depression in Iran's nursing students. Methods: the research was conducted as a systematic review and meta analysis, all published scientific articles related to the prevalence of depression in nursing students were searched in 5 databases (Web of Science, Scopus, PubMed, SID, Magiran) and Google Scholar search engine and then their quality was evaluated. The heterogeneity of the studies was investigated using the I2 index and meta-regression model to evaluate... 

Face Analysis is an important task in image processing. Most of these tasks centralized on face recognition and detection. One of different ways for deceiving automatic face analysis systems is mark notation on the skin. On the other hand some applications attempts to eliminate defects of the face. Hence, in this paper we try to detect and remove skin marks on the face, whether they're natural or not. Our algorithm passes face image through appropriate filters to get mark candidates and then create a graph space using 8-point neighborhood relations of mark candidates image pixels. Then we compute probabilities of each mark candidate using four measures based on intensity of occurrence, shape... 

In this paper, a two-component Lattice Boltzmann Method (LBM) has been utilized to simulate the natural convection of TiO2-water nanofluid in a curved geometry. The main purpose of this research is to study the effect of nanoparticle size and also boundary conditions on the thermal characteristics of the nanofluid. Furthermore, the effect of Rayleigh number (Ra) and volume fraction of nanoparticles (ϕ) on the average Nusselt number (Nuave) have been investigated. Two different thermal boundary conditions, namely adiabatic and constant temperature, have been considered in the current work for the curved boundaries. The Rayleigh number varies from 103 to 109. Four different sizes, namely 10,... 

Noise analysis techniques including Feynman-α (variance-to-mean) and Rossi-α (correlation) have been simulated by MCNP computer code to calculate the prompt neutron decay constant (α0), effective delayed neutron fraction (βeff) and neutron generation time (Λ) in a subcritical condition for the first operating core configuration of Tehran Research Reactor (TRR). The reactor core is considered to be in zero power (reactor power is less than 1 W) in the entire simulation process. The effect of some key parameters such as detector efficiency, detector position and its dead time on the results of simulation has been discussed as well. The results of proposed method in the current study are... 

The phase diagram of the strongly correlated Hubbard model with intrinsic spin-orbit coupling on the honeycomb lattice is explored here. We obtain the low-energy effective model describing the spin degree of freedom. The resulting model is then studied by the Schwinger boson and Schwinger fermion approaches. The Schwinger boson method elucidates the boundary between the spin liquid phase and the magnetically ordered phases, Neel order, and incommensurate Neel order. Increasing the strength of the spin-orbit coupling is shown to narrow the width of the spin liquid region. The Schwinger fermion approach sheds further light on the nature of the spin liquid phase. We obtained three different... 

The inhibition of mild steel corrosion in 0.5 M sulphuric acid by the symmetrical acetylenic alcohol 2- butyne-1,4-diol is investigated. Weight loss and electrochemical impedance data consistently indicate inhibition efficiencies up to 98%. Short-term impedance measurements reveal that the interfacial inhibition is a function of the exposure time, and that full performance is achieved faster as inhibitor concentration and temperature are higher. An infrared study of the surface film provides evidence that the film does not achieve its final state but after several hours. Atomic force Microscopy has been used for investigation the surface topography of metallic electrode. © 2009 by ESG  

Most seismic design codes accept heavy damages to buildings in case of large earthquakes, provided that they are prevented against collapse. However, this leads to unacceptable consequences, such as very large volume of the required reconstruction works, in large populated cities. One way to get rid of these adverse consequences is using the idea of combining rocking/seesaw motion of the building's structure and energy dissipation at base level to create buildings easily repairable even after a large earthquake. In the present study, this idea has been employed for designing steel buildings with seesaw motion capability by using a central massive column at ground floor, with elastic behavior... 

The first step to locate Partial Discharge in power transformers is to find a model that can clearly explain the behavior of the winding in high-frequency. The detailed model is one of the models used for the study of PD. One of the fundamental problems of the described model is to find its parameters. And the accuracy in calculating these parameters has significant impact on reducing the simulation error and PD locating. The current paper seeks to calculate the parameters of the detailed model 20kv distribution transformer winding by using the finite element method (FEM). Comparing the results of this model with pulse waveforms obtained from the PD to the winding in the laboratory... 

To locate accurately the occurrence of a partial discharge in a power transformer winding, a wide frequency band model of the winding is required. In this paper a wide frequency band Multi Conductor Transmission Line model (MTL) is employed to simulate the propagation of PD signal in transformer windings. The MTL model is briefly reviewed and the related equations of the model are reformulated to easily simulate occurrence of a PD signal along the winding. Software is developed in Matlab to calculate the windings resonance frequencies and the magnitudes of over-voltages occurring between different disks along the winding. Then propagation of PD signal in a power transformer (900MVA, 525kV),... 

In this study, novel chitosan/poly(vinyl alcohol) (PVA)/SiO2 nanocomposite ENMs were prepared to improve the mechanical strength and permeation properties of ENMs. The effect of various concentrations of SiO2 in the spinning solution (0, 0.5, 1.0 and 2.0 wt %) on the morphology, fiber diameter, porosity, thermomechanical properties, and permeability of the synthesized membranes was investigated. The prepared affinity membranes were utilized for the removal of dye from colored wastewater. Incorporating SiO2, as a reinforcing agent, was found to increase the compaction resistance of the nanocomposite ENMs. With the addition of 0.5 wt % of SiO2, the Young's modulus of the prepared membranes... 

In this paper, an incompressible smoothed particle hydrodynamics (SPH) method is presented to solve unsteady free-surface flows. Both Newtonian and viscoelastic fluids are considered. In the case of viscoelastic fluids, both the Maxwell and Oldroyd-B models are investigated. The proposed SPH method uses a Poisson pressure equation to satisfy the incompressibility constraints. The solution algorithm is an explicit predictor-corrector scheme and employs an adaptive smoothing length based on density variations. To alleviate the numerical difficulties encountered when fluid is highly stretched, an artificial stress term is incorporated into the momentum equation which reduces the risk of... 

For a structure to show radiative cooling property, it must have first, high reflectivity of above 90% in the wavelength range of 0.3 to 3 μm, and second, high emissivity for the wavelengths ranging from 8 to 13 μm, namely atmospheric transparency window. Being inspired by the architecture of microwave absorbers used extensively for antenna measurements, we proposed a novel microstructure with near unity emissivity that can be further developed for radiative cooling. To this end, we designed and analyzed a V-grooved multilayer periodic microstructure capable of perfectly emitting in the aforementioned wavelength range. Further, SU-8 is selected as the material of the proposed microstructure.... 

A specific structure of doped graphene with substituted silicon impurity is introduced and ab initio density-functional approach is applied for the energy band structure calculation of the proposed structure. Using the band structure calculation for different silicon sites in the host graphene, the effect of silicon concentration and unit cell geometry on the bandgap of the proposed structure is also investigated. Chemically, silicon-doped graphene results in an energy gap as large as 2eV according to density-functional theory calculations. As the authors will show, in contrast to previous bandgap engineering methods, such structure has significant advantages including wide gap tuning... 

Novel montmorillonite (Mt) chitosan/poly(vinyl alcohol) (PVA) nanocomposite electrospun nanofibrous membranes (ENM) were prepared and utilized for the treatment of colored wastewater. The Mt. with different mass percentages (0, 1.0, 2.0 and 3.0 mass%) was added to the membrane structure, and its effect on morphology, pore size, porosity, mechanical strength, and permeation properties of ENM were investigated. The fabricated membranes were used as affinity membranes for dye removal with ultrafast permeating adsorption. The results showed that incorporating Mt. as a reinforcing agent improved the nanocomposite ENM resistance to compaction. Young's modulus for the prepared membranes increased... 

One of the most important issues in planning the "reservoir" type of hydro-power plants (HPP) is to determine the installation capacity of the HPPs and estimate its annual energy value. In this paper, a method is presented. A computer program has been developed to analyze energy calculation and estimation of the most important economic indices of an HPP using the sensitivity analysis method. Another program, developed by Matlab software, calculates the reliability indices for a number of units of an HPP with a specified load duration curve using the Monte Carlo method. Ultimately, comparing the technical, economic and reliability indices will determine the installation capacity of an HPP. By... 

A new model on the evolution of dislocation structure of cell forming metals and alloys through severe plastic deformation is presented. Following previous approaches, the model considers a cellular dislocation structure consisted of two phases: cell interiors and cell walls. The model distinguishes edge and screw dislocations in terms of three categories: mobile dislocations, immobile dislocations in cell interiors and immobile dislocations in cell walls. Then considering physical and geometrical assumptions for each dislocation category, an evolutional law is derived, based on some dislocation interaction mechanisms such as dislocation generation, annihilation, locking and migration. The... 

Since the constitutive information is one of the most important aspects of material deformation analysis, here a new constitutive model is proposed that can investigate the behavior of material during intense deformation better than existent models. The model that is completely based on physical mechanisms can predict all stages of flow stress evolution and also can elucidate the effects of strain and strain rate on flow stress evolution of material during intense plastic deformation. Here as an application, implementation of the constitutive model in finite element method (FEM) is used to compare two methods of sever plastic deformation (SPD) processes of copper sheet; repetitive... 

In this study, a dislocation-based model is presented for investigating the evolution of micro structure and mechanical properties of thin films during a wide range of straining. The model is applied to the High Pressure Torsion (HPT) process of thin nickel disks that provides valuable information on the evolution of material parameters during deformation. The model considers a free surface theory for thin films and can explain the size effect phenomenon in agreement with previous reported trends in literature