Sharif Digital Repository

We synthesized by electrostatic self-assembly route in basic solution Fe3O4–cysteine/RGO and Fe3O4/RGO–cysteine nanocomposites. In this method, electrostatic interaction was created via negatively charged surface of the reduced graphene oxide and reduced graphene oxide–cysteine sheets and positively charged surface of the Fe3O4 and Fe3O4–Cys nanoparticles in aqueous solution. The structural and magnetic properties of the prepared samples were analyzed by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM), respectively. The dependences of magnetization as a function of... 

We synthesized by electrostatic self-assembly route in basic solution Fe3O4–cysteine/RGO and Fe3O4/RGO–cysteine nanocomposites. In this method, electrostatic interaction was created via negatively charged surface of the reduced graphene oxide and reduced graphene oxide–cysteine sheets and positively charged surface of the Fe3O4 and Fe3O4–Cys nanoparticles in aqueous solution. The structural and magnetic properties of the prepared samples were analyzed by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM), respectively. The dependences of magnetization as a function of... 

The excellent photoluminescent properties of Fe3O4-graphene quantum dots (Fe3O4/GQD) nanoparticles prepared at 30 and 90 °C have made them as promising optical probes for imaging. Herein, the cytotoxicity of GQD and Fe3O4/GQD nanoparticles in L929 cells was investigated using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide] assay. The cellular apoptosis or necrosis was then evaluated by flow cytometry analysis. The Fe3O4/GQD nanoparticles were characterized by transmission electron microscopy (TEM), Raman spectroscopy (Raman), Fourier-transform infrared spectroscopy (FT-IR), photoluminescence (PL). Characterization results obtained, clearly show that Fe3O4/GQD nanoparticles... 

Lack of a direct method to control combustion timing is one of the main disadvantages of homogeneous charge compression ignition (HCCI) engines. Fuel blending, in which two fuels with different auto-ignition characteristics are blended, can be used to control combustion timing. Utilizing different additives is another method for HCCI combustion control. The aim of this research is investigation on the effect of reformer gas addition on the availability terms in HCCI engines fueled with primary reference fuels (PRFs). A multi zone model (MZM) coupled with a semi detailed chemical kinetics mechanism is used for calculation of different terms of exergy analysis. Heat and mass transfer between... 

From 1970s, studies have been conducted on the hydraulic design of stepped spillways and many empirical formulas were developed. Despite the simple geometry of these spillways, their hydraulic behavior is complicated. As a result, for many cases, the physical models are studied to verify the design. Numerical simulation is considered as a tool to reduce the laboratory tests, in order to save time and money. Furthermore, the parameters which are not investigated or measured in physical models could be evaluated. In this paper, the results of numerical simulations are compared with the results of physical models and empirical formulas for the spillway of Renwick dam studied in a 1/8 scale... 

(Lanthanum, Cerium)(Iron, Manganese, Cobalt, Palladium)(Oxygen)3- Perovskite catalyst was prepared by the citrate route and deposited on ceramic monoliths via dip coating procedure. The catalyst was applied on a car with XU7 motors and the amount of emission was monitored with vehicle emission test systems in Sapco company. The results were compared with the imported catalyst with noble metals such as palladium, platinum and rhodium by Iran Khodro company based on the Euro III standards. The catalysts were characterized by specific surface area measurements, scanning electron microscopy, X-ray diffraction, line scan and map. In the results, obtained in the home made sample, the amount of... 

Nickel titanium shape memory alloys (NiTi-SMAs) were successfully produced from elemental Ni/Ti powders by powder metallurgical method and then subjected to age treatment. Microstructure was examined by SEM and XRD and phase transformation temperatures were measured by dilatometric method. The phase transformation temperatures increased with both duration and temperature of the age treatment. The porous product exhibited desirable shape memory effect. © 2009 Elsevier B.V. All rights reserved  

We produced bifurcated bone-like shape memory implant (BL-SMI) with desirable tooth-root fixation capability by compact-sintering of TiH2–Ni-urea mixture. The primary constituents of the porous product were Ni and Ti. We could adjust the pores' shape, size, and interconnectivity for favorite bone ingrowth by using urea as a space holder. Without urea, we obtained an average porosity of 0.30, and a mean void size of 100 μm. With 70 vol % urea, we got 62% interconnected pores of 400 μm average size. Aging allowed us to tune the austenite-martensite transformation temperatures towards the needed body tissue arouse. Differential scanning calorimetry measured the transformation temperatures.... 

Drying is a common practice for delaying deterioration, preserving quality, and easier prolonged storage of agricultural products. According to the climatic and geographical conditions of Arsanjan County, Fars, Iran. So far, many studies have been conducted on the design and use of various barriers on absorber plates with the aim of increasing heat exchange and subsequently increasing the efficiency of air heaters and solar dryers. However, the effect of using the metal of the sewing machine bobbin on the performance of these dryers has not been studied yet. Therefore, in this study, for the first time, this metal and also pipes containing PCM (phase change material) were used as a barrier... 

The normal human running has been simulated by two-dimensional biped model with 7 segments. Series of normal running experiments were performed and data of ground reaction forces measured by force plate was analyzed and was fitted to some Fourier series. The model is capable to simulate running for different ages and weights at different running speeds. A proportional derivative control algorithm was employed to grant stabilization during each running step. For calculation of control algorithm coefficients, an optimization method was used which minimized cinematic differences between normal running model and that of the experimentally obtained from running cycle data. This yielded the... 

The current study used the horizontal slices method to develop a new formulation to calculate active pressure on retaining walls. In this method, the failure wedge is assumed to be circular in cohesive-frictional soil. In addition to the formula, graphs are provided to determine the center and radius of failure without need for calculation to determine the pressure exerted on the retaining wall. A comparison of the results of the proposed method with previous methods shows that the active pressure calculated using a circular failure wedge was higher than when using a plate failure wedge; confirming the importance of the circular failure wedge. The proposed method can calculate the shear... 

The g-C3N4/Fe2O3 nanocomposite was produced by the solution combustion synthesis (SCS) of iron-nitrate/g-C3N4 mixtures of varying concentration ratios and using urea as a fuel. The following methods did characterization of the products: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller investigation (BET), ultraviolet–visible light analysis (UV–vis) and photoluminescence measurement (PL). Effect of iron nitrate on stability and photocurrent density under simulated visible-light irradiation was determined. The... 

Luminescence downshifting (LDS) of light can be a practical photon management technique to compensate the narrow absorption band of high-extinction-coefficient dyes in dye-sensitized solar cells (DSSCs). Herein, an optical analysis on the loss mechanisms in a reflective LDS (R-LDS)/DSSC configuration is reported. For squaraine dye (550-700 nm absorption band) and CaAlSiN3:Eu2+ LDS material (550-700 nm emission band), the major loss channels are found to be non-unity luminescence quantum efficiency (QE) and electrolyte absorption. By using an ideal LDS layer (QE=100 %), a less absorbing electrolyte (Co-based), and antireflection coatings, approximately 20% better light harvesting is obtained.... 

In this study, corrosion behaviour of porous NiTi modified by plasma sprayed alumina coating has been investigated. Scanning electron microscopy and X-ray diffraction techniques were applied for the morphology and microstructure characterisation, while linear sweep voltammetry and electrochemical impedance spectroscopy were used for investigation of corrosion behaviour of coated and uncoated NiTi specimens. Induced couple plasma was conducted to measure ion release of the specimens in simulated body fluid at 37°C. The plasma sprayed Al2O3 coating on the porous NiTi improved the surface characteristics for biomedical applications. The alumina coating significantly hampered Ni ion release from... 

In recent years, the mining of cryptocurrencies such as Bitcoin has attracted much global attention due to the simplicity and high profitability of this business, especially in countries with low electricity rates. The process of cryptocurrency mining using cryptocurrency mining devices requires a significant amount of computing power. This industry, which is increasingly growing in energy and carbon emissions, can cause environmental concerns. Common ways to reduce this amount of energy consumption are to prohibit mining and charge these loads at a higher electricity rate; however, these solution methods are not feasible and applicable in many countries. This paper presents an energy... 

In this paper, employing recorded images of multiple cameras, we propose a novel fast approach for three-dimensional (3D) human pose reconstruction. Opening a new framework to the pose estimation application, the proposed method is inspired by optical 3D reconstruction algorithms conventionally used for integral imaging. Thanks to the fact that the pose estimation can be carried out by using only key features of the raw recorded images, the computation time and the complexity of our method are considerably reduced. Furthermore, utilizing the here proposed algorithm, rapid variations in actions can be easily tracked. The validity of the proposed method is demonstrated by several experimental... 

A recyclable optical nanosensor was developed by immobilizing L-tyrosine functionalized silver nanoparticles (AgNPs) on the polyethylene terephthalate (PET) substrate for rapid determination of Pb2+ ions. At first, the L-tyrosine functionalized AgNPs were assessed in the solution phase; the response time was lower than 15 s, and a limit of detection lower than 9 nM was obtained in the dynamic range of 1–1000 nM. For fabrication of the optical assay kit, the design of experiment (DOE) was used to optimize the immobilization efficiency of the nanoparticles on PET films by studying AgNO3 concentration and pH as two crucial parameters. The assay kit in optimal conditions showed a sharp localized... 

The energy supply system of Uzbekistan is not well positioned to meet the rapidly rising domestic energy demand of this country. Uzbekistan's current energy supply system is outdated and has very low diversity, as most of its energy comes from natural gas. In addition to producing immense amounts of greenhouse gas and environmental pollution, this situation is untenable considering the eventual depletion of fossil fuel reserves of this country. Uzbekistan's renewable energy sector is highly undeveloped, a situation that can be attributed to the lack of coherent policies for the advancement of renewable power and the low price of natural gas. However, this country has significant untapped... 

As the emergence of Internet of Things (IoT) brings the realization of ubiquitous connectivity ever closer, our reliance on these applications gets more important. Nowadays, such connected devices could be found everywhere, from home appliances to industrial control systems and environmental monitoring applications. One of the main challenges in IoT infrastructures is that of reliability, which emboldens itself in the context of Low-power and Lossy Networks (LLN) as they are inherently prone to packet loss as a result of their environmental and design constraints. Therefore, reliability of IoT devices becomes crucially important. With communication, the most important consideration in these... 

In this paper, we present a detailed analysis of a two-dimensional lossless and non-dispersive structured conducting interface, which is approximated by a two-dimensional ideal one-component plasma-like conducting sheet enclosed by two isotropic dielectrics. We present a Green's function formalism to analyze the propagation of surface plasmons and find new expressions. We also present analytical extensions of the approach to include loss, and discuss the results and applications of the theory. We study the symmetry properties of eigenmodes and show that the symmetries of the eigenmodes at high-symmetry points of the Brillouin zone are similar to those of the E-polarization eigenmodes of a...