Sharif Digital Repository

A stable capillary liquid jet formed by an electric field is an important physical phenomenon for formation of controllable small droplets, power generation and chemical reactions, printing and patterning, and chemical-biological investigations. In electrohydrodynamics, the well-known Taylor cone-jet has a stability margin within a certain range of the liquid flow rate (Q) and the applied voltage (V). Here, we introduce a simple mechanism to greatly extend the Taylor cone-jet stability margin and produce a very high throughput. For an ethanol cone-jet emitting from a simple nozzle, the stability margin is obtained within 1 kV for low flow rates, decaying with flow rate up to 2 ml/h. By... 

The objective of this paper is to predict the effect of hydrocarbon contamination on the shear strength parameters of sand by using various machine learning platforms. Multilayer perceptron, support vector machine, random forest, gradient boosting method, and multi-output support vector machine were methods used to predict the hydrocarbon contamination impacts on the internal friction angle and cohesion of contaminated sand. Random forest exhibited the best results for cohesion, whereas, for the friction angle, the gradient boosting method outperformed other approaches. Moreover, the multi-output support vector machine yielded better results than those pertaining to a single support vector... 

This study investigates an ethanol liquid jet subjected to combination of an air crossflow and a normal electric field. The results on the liquid jet trajectory and subsequent droplets flight paths are presented. The liquid jet trajectory was found as a function of two non-dimensional quantities; the liquid jet to the crossflow momentum ratio and the electroinertial number. The electroinertial number is defined as the ratio between the liquid jet specific momentum and the electric force. A correlation is introduced for the jet trajectory in low crossflow speeds and electric field intensities. The same two quantities control the detached droplets flight paths. Satellite droplets flight angles... 

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 behavior of an electrified liquid jet breakup and modes of disintegration were investigated at different flow rates and voltages. The current phenomenology belongs to a new injector introduced recently by Morad et al. (2016). This injector has proven to highly extend the stability and flow rate of electrospray particularly in the Taylor cone-jet mode. The experimental investigation was performed using a high-power light-emitting diode (LED) illumination as the light source. The light source was developed to operate in the pulsing condition when synchronized with a digital camera and was particularly designed to function properly in the presence of high electromagnetic interference (EMI).... 

This paper presents a new approach for fuel burn up evaluation and radioactive inventory calculation used in Tehran Research Reactor. The approach is essentially based upon the utilization of a program written by C# which integrates the cell and core calculation codes, i.e., WIMSD-4 and CITVAP, respectively. Calculation of fuel burn up and radioactive inventories has been done for 26 core configuration of Tehran Research Reactor with HEU fuel element. The present inventory and fuel enrichment of each fuel element have been calculated  

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... 

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... 

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... 

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 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,... 

The purpose of the present study is to develop the 3D static and noise simulator based on Galerkin Finite Element Method (GFEM) using the unstructured hexahedral elements. The 3D, 2G neutron diffusion and noise equations are discretized using the unstructured hexahedral by considering the linear approximation of the shape function in each element. The validation of the static calculation is performed via comparison between calculated results and reported data for the VVER-1000 benchmark problem. A sensitivity analysis of the calculation to the element type (unstructured hexahedral or tetrahedron elements) is done. Finally, the neutron noise calculation is performed for the neutron noise...