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density-measurements
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Helical antenna to measure radiated power density around a BTS: Design and implementation
, Article Proceedings of 3rd Asia-Pacific Conference on Antennas and Propagation, APCAP 2014 ; 18 December , 2014 , Pages 185-188 ; Rassaei, F ; Sharif University of Technology
Abstract
A helical antenna is a helical shaped conductor winded around a cylinder. This antenna can radiate in different modes but the axial mode is one of the most commonly used ones since in this mode, it gives the maximum radiation power. This paper presents a novel, simple and inexpensive method to measure the radiated power density around base transceiver stations (BTS). We designed an optimized helical antenna for this application. Our simulation results show that it is possible to measure the power density with about 10% error, which is acceptable for this application. Furthermore, we implemented the designed antenna based on our analytical results and calibrate it. Experimental tests have...
Web graph compression by edge elimination
, Article Data Compression Conference, DCC 2006, Snowbird, UT, 28 March 2006 through 30 March 2006 ; 2006 , Pages 459- ; 10680314 (ISSN) ; Khalili, H ; Nourbakhsh, E ; Ghodsi, M ; Brandeis University ; Sharif University of Technology
2006
In-service corrosion evaluation in pipelines using gamma radiography - A numerical approach
, Article Insight: Non-Destructive Testing and Condition Monitoring ; Volume 46, Issue 7 , 2004 , Pages 396-398 ; 13542575 (ISSN) ; Rastkhah, N ; Kermani, A ; Seidi, M ; Movafeghi, A ; Sharif University of Technology
2004
Abstract
Wall thickness measurement and deterioration determination of 6 and 10 inch pipes due to corrosion/erosion/pitting was evaluated by using radiographic film density measurements. Special reference blocks were prepared with defined step wall reductions and artificial defects. Gamma radiography with a Ir-192 source was used. A double-wall technique with longitudinal film arrangement was used for this purpose. Formulae were developed from the experiments for numerical calculations. It was observed that this method can determine remaining wall thickness as well as pitting corrosion in insulated and non-insulated pipes with differential and absolute density measurements. The purpose of the work...
Density and Level Monitoring and Control in Polypropylene Plants
, M.Sc. Thesis Sharif University of Technology ; Hajsadeghi, Khosrow (Supervisor)
Abstract
Polypropylene plants receive propylene monomer and produce polypropylene polymer by inducing chemical reactions under high pressure and high temperature conditions. In these plants it is essential to monitor and carefully control the density and level of the material contents in slurry high pressure and high temperature reactors and vessels. Due to process conditions and the advantages of the non contact measuring method we use radioactive level and density measurement method specially gamma ray level and density detectors and transmitters in P.P plants. Sometimes, however known and unknown natural or manmade factors may affect the performance of these devices. The known factors such as NORM...
Density Measurement in Oil and Gas Wells using Ultrasonic Sensors
, M.Sc. Thesis Sharif University of Technology ; Movahedian Attar, Hamid (Supervisor)
Abstract
Production logging consists of running measurement instruments called logging tools into an oil or gas well to measure various parameters such as temperature, flow velocity, pressure, density, etc. The primary purpose for production logging is to allow enhancing production profits and decreasing costs. Nowadays the common way for fluid density measurement as a part of these tools depends on radioactive source. Special considerations must be taken upon the use of this principle due to its radioactive character. This thesis is focused on a non-radioactive method of determining density. The subject of this thesis is to consider methods for measuring density based on principle of acoustic...
Numerical simulation of three-dimensional interfacial flows
, Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 17, Issue 4 , 2007 , Pages 384-404 ; 09615539 (ISSN) ; Panahi, R ; Seif, M. S ; Sharif University of Technology
2007
Abstract
Purpose - This study aims to present compatible computational fluid dynamics procedure for calculation of incompressible three-dimensional time-dependent flow with complicated free surface deformation. A computer software is developed and validated using a variety of academic test cases. Design/methodology/approach - Two fluids are modeled as a single continuum with a fluid property jump at the interface by solving a scalar transport equation for volume fraction. In conjunction, the conservation equations for mass and momentum are solved using fractional step method. Here, a finite volume discretisation and colocated arrangement are used. Findings - The developed code results in accurate...
Impact of nonlinear absorption on propagation of microwave in a plasma filled rectangular waveguide
, Article Waves in Random and Complex Media ; Volume 26, Issue 3 , 2016 , Pages 272-283 ; 17455030 (ISSN) ; Vaziri, M ; Rooholamininejad, H ; Bahrampour, A. R ; Sharif University of Technology
Taylor and Francis Ltd
Abstract
In collisional and ponderomotive predominant regimes, the propagation of microwave in rectangular waveguide filled with collisional plasma is investigated numerically. The dominant mode is excited through an evacuated waveguide and then enters a similar and co-axis waveguide filled with plasma. In collisional predominant regime, the amplitude of electric field is oscillated along propagation path; outset of propagation path due to the electron-ion collision, the intensity oscillations are reduced. Afterward, under competition between the collisional nonlinearity and absorption, the intensity is increased, so the electron density peak is created in middle of waveguide. In ponderomotive...
Trap density measurement in three-dimensional nanostructured photoelectrode of titanium dioxide with various morphologies
, Article Applied Physics A: Materials Science and Processing ; Volume 122, Issue 4 , 2016 ; 09478396 (ISSN) ; Mohammadpour, R ; Sharif University of Technology
Springer Verlag
2016
Abstract
Three-dimensional TiO2 nanostructures take advantages of large surface area and superior light-harvesting efficiency, as well as appropriate charge carrier transport and separation features. Here in this research, we report for the first time on measurement of density of localized trap states in three-dimensional TiO2 nanostructures with various morphologies. Bare 1-dimensional TiO2 nanofibers have been synthesized via two different methods: electrospinning and hydrothermal processes. The surface of TiO2 nanofibrous has been modified with nanoparticles and nanobranches thorough second hydrothermal process. Various morphologies of nanostructured TiO2 have been fabricated including...
Effect of reinforcement volume fraction on mechanical alloying of Al-SiC nanocomposite powders
, Article Powder Metallurgy ; Volume 50, Issue 3 , 2007 , Pages 276-282 ; 00325899 (ISSN) ; Simchi, A ; Riedel, R ; Seyed Reihani, S. M ; Sharif University of Technology
2007
Abstract
Mixtures of aluminium powder and nanoscaled SiC particles (n-SiC) at various volume fractions of 0, 1, 3, 5, 7 and 10 are comilled in a high energy planetary ball mill under an argon atmosphere to produce nanocrystalline Al-SiC nanocomposites. High resolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD) method, laser particle size analysis and powder density measurement were used to study the morphological changes and microstructural evolution occurred during mechanical alloying. Al-SiC composite powder with microscaled SiC particles (1 μm) was also synthesised and characterised to examine the influence of reinforcement particle size on the milling process. It was found that...
Generating the optimum self-focusing in the relativistic laser-plasma interaction
, Article IEEE Transactions on Plasma Science ; Volume 41, Issue 5 , 2013 , Pages 1570-1574 ; 00933813 (ISSN) ; Sadighi Bonabi, R ; Sharif University of Technology
2013
Abstract
In this paper, the effect of basic parameters of laser and plasma on controlling self-focusing is investigated, and based on the introduced effective parameter for self-focusing (EPSF), the effects of laser wavelength, the initial spot size of laser beam, the initial intensity of laser, and the plasma electron density on self-focusing are discussed. It is found that the relativistic self-focusing strongly depend on the laser wavelength and the beam intensity. The nonlinear effect of beam intensity on the introduced parameter EPSF indicates that after an increasing region for focusing, the self-focusing effect decreases at ultrarelativistic intensities. The effect of the initial beam spot...
Corrosion behavior of ZrO2-SiO2-Al2O3 refractories in lead silicate glass melts
, Article Journal of the European Ceramic Society ; Volume 31, Issue 5 , 2011 , Pages 715-721 ; 09552219 (ISSN) ; Ahmadi, A ; Kakooei, S ; Sadrnezhaad, S. K ; Sharif University of Technology
2011
Abstract
High-temperature (1200-1350°C) corrosion of fused-cast ZrO2-Al2O3-SiO2 (ZAS) refractory contacting lead silicate glass melt (LSG) containing 68.5wt% PbO was investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), x-ray diffraction (XRD), thickness measurement and Archimedes density measurement. ZAS durability was improved by baddeliyete content and deteriorated with open porosity proportion, corundum percentage and eutectic mixture presence. Diffusion of lead resulted in fusion-temperature lowering of the glassy layers embedded within the ZAS particles. Heating caused viscosity drop across the interface, loosening the...
A novel method for measuring the MTF of CT scanners: A phantom study
, Article 2019 IEEE International Symposium on Medical Measurements and Applications, MeMeA 2019, 26 June 2019 through 28 June 2019 ; 2019 ; 9781538684276 (ISBN) ; Hosseini, S. A ; Reza Ay, M ; Safarzadehamiri, A ; Ghafarian, P ; Zaidi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
The modulation transfer function (MTF) is well known as a crucial parameter in quality assurance of computed tomography (CT) scanners, which provides detailed information of both contrast and resolution of CT images. Different methods have been introduced and developed to calculate the MTF of CT scanners. However, a robust methodology which accurately estimates the MTF of CT scanners under the use of every range of object electron density and tube current-time product (mAs) has not been reported so far. To this aim, a new wavelet-based circular edge method for MTF measurement has been presented in this work. Owning to the edge spread function (ESF) susceptibility to noise, the approach was...
Synchronous measurements of the velocity and concentration in low density turbidity currents using an Acoustic Doppler Velocimeter
, Article Flow Measurement and Instrumentation ; Volume 17, Issue 1 , 2006 , Pages 59-68 ; 09555986 (ISSN) ; Shamsai, A ; Ataie Ashtiani, B ; Sharif University of Technology
2006
Abstract
Low density turbidity currents have been investigated in a laboratory flume. An Acoustic Doppler Velocimeter (ADV) was used to measure the velocity. The dimensionless velocity profiles were compared with previous studies to check the accuracy of acoustic measuring techniques for turbidity currents. Successful use of the ADV to measure the current velocity has led to interest in the technique of using acoustic sensors to estimate concentrations. Acoustic backscattering analyses are used for estimating the sediment concentration in turbidity currents. With this approach, concentration measurements can be reasonably well represented by a similarity profile. Using this technique, an accurate...
Investigating the effect of design parameters on the response time of a highly sensitive microbial hydrogen sulfide biosensor based on oxygen consumption
, Article Biosensors and Bioelectronics ; Volume 70 , 2015 , Pages 106-114 ; 09565663 (ISSN) ; Yazdian, F ; Amoabediny, G ; Hakim, M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
A novel hydrogen sulfide microbial biosensor was developed based on investigating the influence of four design parameters: cell concentration, immobilization bed type, hydrogen sulfide concentration, and geometrical shape of the biosensor. Thiobacillus thioparus was used as the recognition element and it was immobilized on sodium alginate as well as agarose bed. The results were optimized by the application of statistical optimization software based on response time of the system. Oxygen reduction was considered as the detection sign. Sodium alginate solution with a concentration of 2.3% (w/v) and optical density of 10 at 605. nm was found as the optimum conditions for immobilization with...
The electron density distribution and field profile in underdense magnetized plasma
, Article Physics of Plasmas ; Volume 17, Issue 3 , 2010 ; 1070664X (ISSN) ; Etehadi-Abari, M ; Sharif University of Technology
2010
Abstract
In this work propagation of a high frequency electromagnetic wave in underdense plasma in presence of an external magnetic field is investigated. When a constant magnetic field perpendicular to the motion of electrons is applied, then the electrons rotate around the magnetic field lines and generate electromagnetic part in the wake with a nonzero group velocity. By using of the Maxwell equations and nonlinear differential equation for the electric field a direct one-dimensional (1D) procedure for calculating hydrodynamic equations are developed and the electric and magnetic field profiles in the plasma are investigated. It is shown that by using the external (dc) magnetic field in constant...
In situ synthesis of nanocrystalline Al6063 matrix nanocomposite powder via reactive mechanical alloying
, Article Materials Science and Engineering A ; Volume 527, Issue 18-19 , 2010 , Pages 4897-4905 ; 09215093 (ISSN) ; Simchi, A ; Kim, H. S ; Sharif University of Technology
2010
Abstract
In this work, nanocrystalline Al6063 composite powder reinforced with nanometric oxide ceramic particles was synthesized via an in situ solid-gas reaction during high-energy mechanical alloying under a mixture of argon-oxygen atmosphere. The effect of oxygen volume fraction on the morphological evolution and microstructural changes during mechanical alloying was studied by various analytical techniques including optical and electron microscopy, X-ray diffraction, laser particle size analysis, apparent density measurement, and microhardness test. The reactive mechanical alloying resulted in the formation of amorphous Al- and Al-Mg-Si-Fe oxides with a size range of 40-100. nm and volume...