Sharif Digital Repository

This work aims to develop a nonlinear layerwise shell element formulation for shear-deformable laminated composite plate and shell structures. The element is formulated based on a zigzag theory in presence of individual local coordinates in the thickness direction for separate layers. In order to properly employ the zigzag theory, the considered local coordinates have different ranges of variation for middle, upper and lower layers. Using Mindlin-Reissner theory a convenient displacement field is derived for each layer and an ordered algorithm is adapted to calculate increments in the director vector of each layer due to relative finite rotations of its adjacent layers. Employing this shear... 

In this study, nanostructure zinc oxide (ZnO) films with different thicknesses were sprayed on glass substrates by controlling deposition time. Morphology and roughness of the films were investigated with scanning electron and atomic force microscopes as well as X-ray diffractometer. Considering with structure and surface roughness, two different growth modes as a function of spray time were determined: lateral and vertical modes which were illustrated schematically. Optical properties including photoluminescence, transmission, optical band gap and refractive index as a function of film's thickness and structure were studied. It was observed that the average transmittance is more than 80% in... 

In the present work we report an approach to resistive hydrogen sensing based on graphene quantum dots(GQDs)/WO3 thin films that work reproducibly at low temperatures. GQDs were chemically synthesized and evenly dispersed in WO3 solution with 1:1 molar ratio. The structural evaluation and crystallization of the prepared films was studied by X-ray diffraction, Raman and scanning electron microscopy (SEM) techniques. The SEM images showed uniform distribution of the GQDs in WO3 films with sizes around 50 nm. Raman experiment showed the GQDs are partially reduced with high edge defects as hydroxyl and carboxyl groups which involve both in bridging between WO3 grains via bindings as well as... 

In the present study, we designed a pH-responsive drug nanocarrier based on polyamidoamine-modified Fe3O4 nanoparticles coated by PEGylated starch-co-poly(acrylic acid). This carrier was used for the controlled release of doxorubicin as an anticancer drug model. The purpose of using the polyethylene glycol moiety is to generate a biostable nanocarrier in blood stream as it has been reported widely in the pharmaceutical literature. The use of a poly(acrylic acid) segment also provided pH-sensitivity to the polymer. Besides, the magnetic nanoparticles facilitate the cancer cell targeting with an external magnetic field located near the tumor site. This carrier was... 

In drilling industry, barite particles settling and barite sag as a major problem can potentially impose significant operational issues. Static conditions, in which well undergoes an extended shut-in period, could occur during different drilling and completion operations such fishing operation, tripping, and logging. Despite its importance, such phenomenon is not well understood yet. To avoid issues related to barite settlement and barite sag, a good understanding of the impact of different drilling parameters on barite settlement and sag phenomenon is required. Recently, the mathematical formulation and modeling of settlement and sag processes have gained more attention. In order to better... 

A new triple-component sensor for detection of H2 was developed based on porous silicon and CNTs. An increase in deposition of CVD catalysis was shown to promote a high and fast response. Also, it was shown that the composite system exhibited good selectivity  

Kinetics of air oxidation of MgO-C-Al refractory at 600°-1300°C were investigated using the software based on the modifled shrinking core model (KDA). Commercial bricks containing 88.5% MgO, 10% residual carbon, and 1.5% aluminum anti-oxidant were oxidized isothermally with air. Combination of experimental data with model calculations indicated gas diffusion through solid material and pores as a major controlling step. Previously observed chemisorption process was eliminated from the rate-controlling mechanism with addition of aluminum antioxidant. Comprehensive rate equations were devised for MgO-C-Al and MgO-C oxidation reactions. Overall activation energies of Q id (internal diffusion) =... 

The synthesis and catalytic behavior of palladium loaded magnetic nanocomposite based on natural polysaccharide salep modified with poly (amino pyridine) is described. The synthesized support is loaded with relatively large amounts of palladium ions (0.34mmol g−1). This is a simple, ecologically safe and cost-effective route for the preparation of the novel heterogeneous catalyst that shows high activity for Suzuki coupling reactions under remarkably mild conditions. Furthermore, the prepared catalyst is magnetically recovered and effectively reused for seven cycles of reactions without significant loss of its catalytic activity and loaded palladium nanoparticles. © 2017  

Ancillary services in interconnected networks are crucial to secure real power transfers, maintaining network reliability, improving power quality as well as network stability. Reactive power has always been of special importance as one of the most substantial ancillary services required to control the voltage in power grid. This paper presents a fresh reactive power pricing approach by embedding variable transformer taps into voltage ampere reactive (var) pricing method. To carry out the resultant optimization problem with a set of complicating constraints, the genetic algorithm takes part and guarantees the global optimal solution. The simulation results show that when transformer tap... 

Pursuing a sensing structure with a large effective surface area, partial ordered arrays of ZnO nanorods with flower-like structures are introduced for gas sensing applications. Room temperature H2S response of the grown structure shows significant enhancement after modification with Au nanoparticles. High response (about 1270 at 6 ppm H2S gas) and selectivity were achieved by depositing an Au layer with nominal thickness ∼6 nm. X-ray photoelectron spectroscopy (XPS) was utilized to describe the H2S sensing mechanism  

Titanium oxide (TiO2)-based photodetectors were fabricated using a thermal oxidation technique. The effect of two different annealing temperatures on morphology, structure, and I-V characteristics has been investigated. TiO2/Si heterostructure exhibited diode-like rectifying I-V behavior both in dark and under illumination. Dependence in photoresponse on annealing temperature was observed that was related to effective surface area of quasi-one-dimensional TiO2 nanostructures. Fabricated TiO2/Si diodes in 850 °C as the lower annealing temperature showed higher responsivity and sensitivity compared with grown ones in 950 °C (R850 °C/R950 °C ∼ 5 and S850 °C/S950 °C ∼ 1.6). Rather good... 

Three-dimensional reduced graphene oxide (3D-rGO) structures decorated with CuO particles (GCu) are synthesized through a simple and scalable method for detection of hydrogen sulfide (H2S) gas. For characterization and investigation of porous structure various techniques were employed. Decorated 3D structures demonstrated higher sensitivity and selectivity in comparison to pure structure. Optimized structure for sensing was obtained through introducing different amounts of CuO. The GCu heterostructures containing 35 μmol of CuO powder demonstrated reproducible response of about 30% to the concentration of 10 ppm at room temperature, while complete recovery was obtained through heating to 150... 

The main purpose of this study is to provide the heating power for space heating and sanitary hot water for a residential house in sixteen stations located in Belgium using evacuated tube solar water (ETSW). A one-year dynamic simulation was performed using TSOL 5.5 software and Meteonorm 7.1 was used to obtain the climatic data. Technical and environmental studies as well as station rankings are the parameters that have been examined for the first time in the present study. The weighting results of using the Best-Worst method (BWM) revealed that total solar fraction and CO2 emission avoided have the highest and lowest weight, respectively. Station ranking was performed using ARAS technique... 

Highly sensitive flexible humidity sensors based on graphene quantum dots (GQDs) were developed. The GQDs were prepared using a facile hydrothermal method and characterized considering morphological, structural, and compositional experiments. Then, their humidity sensing properties in correlation with flexibility characteristics were investigated. Good selectivity and response (∼390 for a RH change of 99%), broad detection range (1-100% RH), rather short response and recovery times (12 and 43 s, respectively) as well as flexibility were obtained, demonstrating that the GQD sensors have potential for application in wearable electronics and RH monitoring. Detection of hydrogen (H2) gas by the... 

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... 

Introduction: Porous 3D scaffolds synthesized using biocompatible and biodegradable materials could provide suitable microenvironment and mechanical support for optimal cell growth and function. The effect of the scaffold porosity on the mechanical properties, as well as the TiO2 nanoparticles addition on the bioactivity, antimicrobial, photocatalytic, and cytotoxicity properties of scaffolds were investigated. Methods: In the present study, porous scaffolds consisting poly (lactide-co-glycolide) (PLGA) containing TiO2 nanoparticles were fabricated via air-liquid foaming technique, which is a novel method and has more advantages due to not using additives for nucleation compared to former... 

Text processing, as one of the main issues in the field of artificial intelligence, has received a lot of attention in recent decades. Numerous methods and algorithms are proposed to address the task of semantic textual similarity which is one of the sub-branches of text processing. Due to the special features of the Persian language and its non-standard writing system, finding semantic similarity is an even more challenging task in Persian. On the other hand, producing a proper corpus that can be used for training a model for finding semantic similarities, is of great importance. In this study, the main purpose is to propose a method for measuring the semantic similarity between short... 

The nitrate-citrate gel exhibits auto-catalytic behavior, which can be used to synthesize nanocrystalline YIG powders. In this study, yttrium iron garnet (Y3Fe5O12) nanocrystalline powders were prepared by a sol-gel auto-combustion process. The influence of metal nitrates to citric acid molar ratio (MN/CA) of the precursor solution on the combustion behavior and crystallite size of synthesized powders was investigated by scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and X-ray diffraction (XRD). The results show that with increasing MN/CA value, the combustion rate increases and the single-phase YIG forms at a higher temperature. The crystallite size of the single phase YIG... 

Nanocrystalline Y3-xMMxFe5O12 powders (MM denotes Misch-metal, x = 0.0, 0.25, 0.5, 0.75, and 1.0) were synthesized by a sol-gel combustion method. Magnetic properties and crystalline structures were investigated using X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), and a scanning electron microscope. The XRD patterns showed that the single-phase garnet of Y3-xMMxFe5O12 was formed at x values ≤ 1.0. The saturation magnetization of powders increased with decreasing MM content and reached the maximum value at Y3 Fe5O12. The crystallite size of powders calcined at 800°C for 3 h was in the range of 38-53 nm. © 2008 American Ceramic Society  

The nitrate-citrate gels exhibit auto-catalytic behavior, which can be used to synthesize the nanocrystalline YIG powders. In this study yttrium iron garnet (Y3Fe5O12) nanocrystalline powders were prepared by a sol-gel auto-combustion process. The influence of pH value of the precursor solution on the combustion behavior and the garnet phase formation of synthesized powders were investigated by scanning electron microscopy (SEM), thermal analysis (DTA/TGA), infrared (IR) spectroscopy and X-ray diffraction technique (XRD). The results show that with increasing pH value, the combustion rate increases. The as-burnt powder prepared with pH 1 yielded a single phase YIG after calcination at 800...