Search for: density--specific-gravity
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    Three-parameter correlation functions for the calculation of thermal conductivity of gases, liquids, and refrigerants over wide temperature-pressure ranges

    , Article High Temperatures - High Pressures ; Volume 35-36, Issue 3 , 2003 , Pages 313-319 ; 00181544 (ISSN) Ghayeb, Y ; Najafi, B ; Daneshmand, E ; Parsafar, G. A ; Sharif University of Technology
    Two new correlation functions with three adjustable parameters for the calculation of thermal conductivity of gases, liquids, and refrigerants over wide temperature-pressure ranges are presented. It is shown that by using suitable mathematical expressions for the correlation functions, the number of adjustable parameters can be limited to three, which is less than for similar functions. The average and maximum deviation of the correlation compared with the measured data is about 1% and 8%, respectively  

    Density and power graphs in graph homomorphism problem

    , Article Discrete Mathematics ; Volume 308, Issue 17 , 6 September , 2008 , Pages 4027-4030 ; 0012365X (ISSN) Daneshgar, A ; Hajiabolhassan, H ; Sharif University of Technology
    We introduce two necessary conditions for the existence of graph homomorphisms based on the concepts of density and power graph. As corollaries, we obtain a lower bound for the fractional chromatic number, and we set forward elementary proofs of the facts that the circular chromatic number of the Petersen graph is equal to three and the fact that the Coxeter graph is a core. © 2007 Elsevier B.V. All rights reserved  

    The prediction of the density of undersaturated crude oil using multilayer feed-forward back-propagation perceptron

    , Article Petroleum Science and Technology ; Volume 30, Issue 1 , 2011 , Pages 89-99 ; 10916466 (ISSN) Rostami, H ; Shahkarami, A ; Azin, R ; Sharif University of Technology
    Crude oil density is an important thermodynamic property in simulation processes and design of equipment. Using laboratory methods to measure crude oil density is costly and time consuming; thus, predicting the density of crude oil using modeling is cost-effective. In this article, we develop a neural network-based model to predict the density of undersaturated crude oil. We compare our results with previous works and show that our method outperforms them  

    Damage evolution in Saffil alumina short-fibre reinforced aluminium during tensile testing

    , Article Materials Science and Engineering A ; Volume 395, Issue 1-2 , 2005 , Pages 27-34 ; 09215093 (ISSN) Tavangar, R ; Weber, L ; Mortensen, A ; Sharif University of Technology
    The evolution of microstructural damage during tensile deformation of pure aluminium reinforced with 10 vol.% alumina short fibres is studied by monitoring the evolution of density and Young's modulus as a function of tensile strain. It is found that Young's modulus drops rapidly until a strain εc ≈ 3%. The composite density remains virtually unchanged in this strain range. At strains above εc, Young's modulus decreases more slowly while the density begins to decrease linearly, indicating void growth in the composite. It is shown that the drop in Young's modulus is linked to fragmentation of fibres aligned along the stress axis, while the decrease in density is related to void opening across... 

    Thin-layer effects on the CPT qc measurement

    , Article Canadian Geotechnical Journal ; Volume 42, Issue 5 , 2005 , Pages 1302-1317 ; 00083674 (ISSN) Ahmadi, M. M ; Robertson, P. K ; Sharif University of Technology
    A numerical analysis is presented to model the cone penetration test (CPT) tip resistance in layered soil. Analyses are performed for two-layer soils composed of either sands with different relative densities or different materials (sand and clay). Parametric numerical modeling is used to determine the distance that a cone senses a new upcoming soil layer interface or a layer interface behind. Analyses are also carried out for a thin sand layer embedded in soft clay. It is seen that the full tip resistance may not be reached in thin stiff layers. This is especially true for penetration in thin dense sand layers interbedded in softer clay. A correction factor is suggested to correct the cone... 

    A new cubic equation of state for sweet and sour natural gases even when composition is unknown

    , Article Fuel ; Vol. 134, issue , 2014 , pp. 333-342 ; ISSN: 00162361 Jarrahian, A ; Heidaryan, E ; Sharif University of Technology
    In this paper, the Heidaryan and Jarrahian equation of state (Heidaryan and Jarrahian, 2013) has been adapted as a first worldwide cubic EOS to calculate the density of dry natural gases, wet natural gases, and single-phase gas condensates "sweet and sour mixtures" (up to 73.85, 97.63 and 38.37 mol percent of H2S, CO2, and N2 respectively) even when the gas composition is unknown, through new gas specific gravity correlation equations. Correction terms of water content as high as 10 mol percent of H2O and hythane (natural gas + hydrogen) as high as 74.9 mol percent of H2 were obtained. The equation of state was validated with 8985 experimental compressibility factor data points from 308... 

    Investigating the rheological properties of nanofluids of water/hybrid nanostructure of spherical silica/MWCNT

    , Article Thermochimica Acta ; Volume 578 , 20 February , 2014 , Pages 53-58 ; ISSN: 00406031 Baghbanzadeh, M ; Rashidi, A ; Soleimanisalim, A. H ; Rashtchian, D ; Sharif University of Technology
    Regarding the importance of rheological properties of water based drilling fluids, the effects of silica nanospheres, multiwall carbon nanotubes (MWCNTs) and two types of their hybrid, i.e. H1 (80 wt.% silica nanosphere/20 wt.% MWCNT) and H2 (50 wt.% silica nanosphere/50 wt.% MWCNT) on the viscosity and density of distilled water were investigated. According to the results, viscosity and density of the nanofluids increased with the concentration, while they were reduced by increasing the temperature. At high concentrations, the least increase in the viscosity of distilled water by adding the nanomaterials is related to H2 (8.2% increase at 1.0 wt.%). Likewise, the optimum operating... 

    Effect of TiO2 nanofiber density on organic-inorganic based hybrid solar cells

    , Article International Journal of Engineering, Transactions A: Basics ; Vol. 27, issue. 7 , 2014 , p. 1133-1138 Boroumandnia, A ; Kasaeian, A. B ; Nikfarjam, A. R ; Mohammadpour, R ; Sharif University of Technology
    In this work, a comparative study of hybrid solar cells based on P3HT and TiO2 nanofibers was accomplished. Electrospinning, a low cost production method for large area nanofibrous films, was employed to fabricate the organic-inorganic hybrid solar cells based on poly (3-hexylthiophene) and TiO2 nanofibers. The performance of the hybrid solar cells was analyzed for four density levels of TiO2 nanofibers which resulted in the average power conversion efficiency of about 0.0134% under AM 1.5 simulated illuminations (100 mWcm-2). It is found that the higher densities of TiO2 lead to more interface area and generating exciton, so the power conversion efficiency will be increased till the active... 

    Modified Redlich-Kwong equation of state for supercritical carbon dioxide

    , Article Journal of Supercritical Fluids ; Volume 81 , September , 2013 , Pages 92-98 ; 08968446 (ISSN) Heidaryan, E ; Jarrahian, A ; Sharif University of Technology
    A new simple and explicit reduced temperature and reduced pressure function has been proposed in the present study for modifying Redlich-Kwong equation of state (EoS) to calculate the density of carbon dioxide in the supercritical region. The average absolute error of the model was found to be 1.63 and 2.07% in the comparison with the literature and NIST density data respectively, which demonstrates superiority of the model over other EoSs  

    Effect of sintering temperature and siliconcarbide fraction on density, mechanical properties and fracture mode of alumina-silicon carbide micro/nanocomposites

    , Article Materials and Design ; Volume 37 , May , 2012 , Pages 251-255 ; 02641275 (ISSN) Rahimnejad Yazdi, A ; Baharvandi, H ; Abdizadeh, H ; Purasad, J ; Fathi, A ; Ahmadi, H ; Sharif University of Technology
    In this study Al2O3-SiC micro/nanocomposites have been fabricated by mixing alumina nanopowders and silicon carbide micro/nanopowders, followed by hot pressing at 1550, 1600, 1650 and 1700°C. The density, mechanical properties and fracture mode of Al2O3-SiC composites containing different volume fractions (2.5%, 5%, 7.5%, 10% and 15%) of micro/nanoscale SiC particles were investigated and compared with those of alumina. The relative density of composites could reach values very close to theoretical density, especially after sintering at 1700°C. However, relative density declined by increasing the SiC fraction at the same sintering temperature. The flexural strength of composites was best for... 

    A suction-controlled ring device to measure the coefficient of lateral soil pressure in unsaturated soils

    , Article Geotechnical Testing Journal ; Volume 44, Issue 1 , 2020 Pirjalili, A ; Garakani, A. A ; Golshani, A ; Mirzaii, A ; Sharif University of Technology
    ASTM International  2020
    A suction-controlled ring device has been developed to continuously measure the coefficient of lateral soil pressure in deformable unsaturated soil samples from the at-rest to the active condition under application of increasing vertical pressure and controlled matric suction. The device incorporates a thin aluminum specimen ring equipped with horizontal strain gages for recording the lateral soil strains. In addition, a sensor recording water volume changes is utilized to continuously monitor the degree of saturation of the soil sample during tests. The matric suction within the soil texture is controlled using the axis translation technique. In order to verify the performance of the ring... 

    Effect of processing parameters on electrical, mechanical and magnetic properties of iron-resin soft magnetic composite

    , Article Powder Metallurgy ; Volume 50, Issue 1 , 2007 , Pages 86-90 ; 00325899 (ISSN) Hemmati, I ; Madaah Hosseini, H. R ; Miraghaei, S ; Sharif University of Technology
    In the present paper, a practical thermal treatment process has been introduced to stress relieve the iron powders in a soft magnetic composite. The composites were pressed and treated at different pressures and temperatures. Also, some of the samples were treated for various periods of time at 200°C. Density, electrical resistivity and transverse rupture strength of the samples were measured and fracture surfaces were studied by SEM. A series of tests were performed to determine the DC magnetic properties of the samples. It has been shown that there are optimum amounts of resin content and compaction pressure and temperature, rather than time is the dominant factor in stress relief of the... 

    Estimation of mean radius, length and density of microvasculature using diffusion and perfusion MRI

    , Article Scientia Iranica ; Volume 13, Issue 4 , 2006 , Pages 348-354 ; 10263098 (ISSN) Ashoor, M ; Jahed, M ; Chopp, M ; Mireshghi, A ; Sharif University of Technology
    Sharif University of Technology  2006
    In theory, diffusion and perfusion information in MRI maps can be combined to yield morphological information, such as capillary density, volume and possibly capillary plasma velocity. This paper suggests a new method for determination of mean radius, length and capillary density in normal regions using diffusion and perfusion MRI. Mean Transit Time (MTT), Cerebral Blood Volume (CBV), Apparent Diffusion Coefficient (ADC), pseudo-diffusion coefficient (D*) and ΔR2 and ΔR2* values were utilized to calculate mean radius, length and capillary density. To verify the proposed theory, a special protocol was designed and tested on normal regions of a male Wistar rat using obtained functions. Mean... 

    Numerical simulation of density current using two-phase flow

    , Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) Afshin, H ; Firoozabadi, B ; Sharif University of Technology
    Due to shear layer at the interface of density current and ambient fluid, density current disturbs and entrains the surrounding fluid. Most existing analytical and numerical models for density current flows are based on the equations for single-phase flows. In this research, the density current has been modeled with two-phase flow model. The governing equations are continuity, x- momentum, and y- momentum equations for every fluid. The volume-of-fluid (VOF) interface tracking technique which uses a piecewise-linear interface calculation (PLIC) in each cell is used to determine the deformation of free surface in density current, numerically. Surface tension is implemented by the continuous... 

    The effect of polymeric surfactant content on the mechanical properties of Al/GNP nanocomposites

    , Article Materials Chemistry and Physics ; Volume 257 , 2021 ; 02540584 (ISSN) Moradi, M ; Abouchenari, A ; Pudine, M ; Sharifianjazi, F ; Sharif University of Technology
    Elsevier Ltd  2021
    Graphene nanoplatelets (GNPs) are ideal reinforcements for improving the mechanical properties of aluminum-based matrices due to their outstanding properties. However, it essentially depends on their uniform dispersion in the matrix. In this study, the challenge of uniform dispersion of graphene was performed by functionalizing the non-covalent surface and sonication of GNPs applying non-ionic polymeric ethyl cellulose (EC) surfactant, in which a colloidal mixture was provided with Al powder and graphene, followed by sintering at 620 °C and consolidation. The density and mechanical properties of nanocomposite specimens were investigated and compared with a non-surfactant-assisted Al/GNP... 

    Direct metal laser sintering of Fe-C-Cu steel powder

    , Article European Powder Metallurgy Congress and Exhibition, Euro PM 2005, Prague, 2 October 2005 through 5 October 2005 ; Volume 3 , 2005 , Pages 41-47 ; 9781899072187 (ISBN) Simchi, A ; Petzoldt, F ; Pohl, H ; European Powder Metallurgy Association ; Sharif University of Technology
    European Powder Metallurgy Association (EPMA)  2005
    Cu-alloyed sintered steels are one of the main product groups in ferrous powder metallurgy (P/M). To expand the application of P/M technology to different sectors of industry and to create new market, it is believed that rapid prototyping and short serial production of sintered parts for functional testing is important. In the present work, rapid prototyping of sintered Fe-C-Cu steel powders by direct metal laser sintering (DMLS) process was studied. Fe, Fe-0.8%C, Fe-2%Cu, Fe-4%Cu, Fe-0.8%C-2%Cu-0.35%P powders were laser sintered in widely varying conditions. The densification and microstructural features of the sintered parts were evaluated. The results revealed that rapid prototyping of... 

    Reducing extent of cracks and increasing time to failure of concrete gravity dams by optimization of properties of layers of concrete

    , Article Scientia Iranica ; Vol. 21, issue. 1 , 2014 , pp. 67-81 ; ISSN: 10263098 ; e-ISSN :2345-3605 Joghataie, A ; Dizaji, M. S ; Sharif University of Technology
    The objective of this paper is to study the improvement in the seismic behavior of concrete gravity dams by optimization of concrete mechanical properties. The criteria to measure the improvement have been: 1) reduction in the extent of cracks and 2) increase in the amount of time dams are able to tolerate earthquakes before failure. The mechanical properties considered have included the density and modulus of elasticity of concrete. The Pine Flat Dam has been selected for this numerical study. During a high intensity earthquake, dams enter a nonlinear phase, where the cracks open and close repeatedly. A smeared crack model has been used for simulation of nonlinearity. For the purpose of... 

    Experimental study of a solar desalination pond as second stage in proposed zero discharge desalination process

    , Article Solar Energy ; Volume 97 , 2013 , Pages 138-146 ; 0038092X (ISSN) Farahbod, F ; Mowla, D ; Jafari Nasr, M. R ; Soltanieh, M ; Sharif University of Technology
    This work represents the efficiency of a solar desalination pond as a second stage of proposed zero discharge desalination processes to reach fresh water and also concentrated brine from the effluent wastewater of the desalination unit of Mobin petrochemical complex. So a solar desalination pond is constructed after a pretreatment unit to concentrate the softened wastewater to about 20wt%. The concentrated wastewater is as a suited feed for a forced circulation crystallizer. During one year, the effects of major parameters such as ambient temperature and solar insolation rate are investigated, experimentally. specific gravity in each layer of concentrated brine wastewater is evaluated. Also,... 

    The effects of nano Mgo on physical and mechanical properties of Al 2O3-SiC composites

    , Article Journal of Ceramic Science and Technology ; Volume 3, Issue 1 , 2012 , Pages 29-34 ; 21909385 (ISSN) Nemati, A ; Surani, F ; Abdizadeh, H ; Baharvandi, H. R ; Sharif University of Technology
    In this research, the effects of nano-sized MgO in Al2O 3-SiC composites were investigated. The overall changes in the density and mechanical properties of sintered samples (hardness, bending strength and toughness) were evaluated. After mixing, drying and uniaxial compaction of the powders, they were first heat-treated at low temperature in an electric furnace to remove any residuals. They were then heat-treated at high temperature (1700 °C) inside a graphite furnace in argon atmosphere for sintering (at normal and high pressure). The content of MgO in the Al 2O3-10 vol% SiC composite was 0, 500, 1000, and 1500 ppm. Thefracture toughness(KIC)of sintered composite with 10... 

    Investigation on the characteristics of micro- and nano-structured W-15 wt.%Cu composites prepared by powder metallurgy route

    , Article International Journal of Refractory Metals and Hard Materials ; Volume 30, Issue 1 , 2012 , Pages 145-151 ; 02634368 (ISSN) Abbaszadeh, H ; Masoudi, A ; Safabinesh, H ; Takestani, M ; Sharif University of Technology
    The properties of W-15 wt.%Cu composites were investigated by preparing two distinct composites of micrometer and nanoscale structures. Micrometer composite was produced by mixing elemental W and Cu powders and nanometer one was synthesized through a mechanochemical reaction between WO3 and CuO powders. Subsequent compaction and sintering process was performed to ensure maximum possible densification at 1000-1200 °C temperatures. Finally, the behavior of produced samples including relative density, hardness, compressive strength, electrical conductivity, coefficient of thermal expansion (CTE) and room temperature corrosion resistance were examined. Among the composites, nano-structured...