Search for: particles--particulate-matter
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    How particle shape affects the flow through granular materials

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 85, Issue 3 , 2012 ; 15393755 (ISSN) Nemati Hayati, A ; Ahmadi, M. M ; Mohammadi, S
    Flow through the pores of granular materials has many instances in practice. Therefore, it is interesting to realize how some parameters, such as the shape of the particles affect the passing flow. Following the recent mathematical theory proposed by the authors, this paper deals with the issue of how tortuosity and permeability are influenced by the particle shape. Comparison of the results with the experimental data reveals the competency of the theory in predicting the impact of particle geometry  

    Comparison of 2_D turbulent particle laden density current and wall jets

    , 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) Hormozi, S ; Firoozabadi, B ; Ghasvari Jahromi, H ; Afshin, H ; Sharif University of Technology
    Dense underflows are continuous currents, which move down the slope due to the fact that, their density are heavier than ambient water. In turbidity currents the density differences arises from suspended solids. Vicinity of the wall make density currents and wall jets similar in some sense but Variation of density cause this flows more complex than wall jets. An improved form of 'near-wall' k-ε turbulence model is chosen which preserve all characteristics of both density and wall jet currents and a compression is made between them. Then the outcomes from low Reynolds number k-ε model is compared with v2̄-f model which show similarity. Also results show good agreement with experimental data... 

    Coarse-grained interaction potentials for anisotropic molecules

    , Article Journal of Chemical Physics ; Volume 124, Issue 17 , 2006 ; 00219606 (ISSN) Babadi, M ; Everaers, R ; Ejtehadi, M. R ; Sharif University of Technology
    We have proposed an efficient parametrization method for a recent variant of the Gay Berne potential for dissimilar and biaxial particles [Phys. Rev. E 67, 041710 (2003)] and demonstrated it for a set of small organic molecules. Compared with the previously proposed coarse-grained models, the new potential exhibits a superior performance in close contact and large distant interactions. The repercussions of thermal vibrations and elasticity have been studied through a statistical method. The study justifies that the potential of mean force is representable with the same functional form, extending the application of this coarse-grained description to a broader range of molecules. Moreover, the... 

    Magnetic anisotropies in FeCo fine particles

    , Article Journal of Magnetism and Magnetic Materials ; Volume 300, Issue 2 , 2006 , Pages 525-531 ; 03048853 (ISSN) Zoriasatain, S ; Azarkharman, F ; Sebt, S. A ; Akhavan, M ; Sharif University of Technology
    The single-domain particles, especially FeCo fine particles have many applications in magnetic information technology. We have prepared Fe 1-xCox fine particles for different x by borohydride method and measured the magnetic and structural properties of the samples. We have then determined the variations of coercivity and anisotropy energy versus x in Fe1-xCox fine particles. The obtained results have been analyzed on the basis of various magnetic anisotropies. Magnetic anisotropies affect the coercivity of the medium for each x as follows: shape and crystal anisotropies for x=0, surface and crystal anisotropies for x=1, shape, induced and crystal anisotropies for x=0.3 and 0.5, and shape... 

    Elastic solids with high concentration of arbitrarily oriented multiphase particles

    , Article Acta Mechanica ; Volume 189, Issue 3-4 , 2007 , Pages 125-139 ; 00015970 (ISSN) Roumi, F ; Shodja, H. M ; Sharif University of Technology
    Springer-Verlag Wien  2007
    The effective properties of elastic solids are strongly linked to their interacting micro-constituent phases. For materials containing dilute distributions of single-phase inhomogeneities, the overall behavior can be estimated in a straightforward manner. But in the non-dilute case, due to the complex inter-particle and particle-matrix interactions the treatment is rather involved. When the particles are heterogeneous, not only become the mentioned interactions more complex, but must properly account for the intra-particle interactions as well. The present work addresses an analytical approach to determine the overall moduli of elastic solids containing random distributions of arbitrarily... 

    Analytical Solution for Isothermal Flow in a Shock Tube Containing Rigid Granular Material

    , Article Transport in Porous Media ; Volume 93, Issue 1 , 2012 , Pages 13-27 ; 01693913 (ISSN) Hayati, A. N ; Ahmadi, M. M ; Mohammadi, S ; Sharif University of Technology
    Analytical solution of shock wave propagation in pure gas in a shock tube is usually addressed in gas dynamics. However, such a solution for granular media is complex due to the inclusion of parameters relating to particles configuration within the medium, which affect the balance equations. In this article, an analytical solution for isothermal shock wave propagation in an isotropic homogenous rigid granular material is presented, and a closed-form solution is obtained for the case of weak shock waves. Fluid mass and momentum equations are first written in wave and (mathematical) non-conservation forms. Afterwards by redefining the sound speed of the gas flowing inside the pores, an... 

    Effect of supply/exhaust diffuser configurations on the contaminant distribution in ultra clean environments: Eulerian and Lagrangian approaches

    , Article Energy and Buildings ; Volume 127 , 2016 , Pages 648-657 ; 03787788 (ISSN) Eslami, J ; Abbassi, A ; Saidi, M. H ; Bahrami, M ; Sharif University of Technology
    Elsevier Ltd 
    In this research, the airflow pattern and particle dispersion in a contaminated full-scale cleanroom are investigated numerically using both Eulerian and Lagrangian approaches. Three different supply diffuser configurations namely (1) central, (2) horizontal and (3) vertical and three different exhaust grille configurations namely (4) vertical symmetric, (5) asymmetric and (6) horizontal symmetric are selected for the analysis. The presented results reveal that the supply/exhaust openings arrangement has a significant influence on the particulate contaminant dispersion in the cleanrooms. The comparison of the above different supply diffuser configurations shows that the vertical and... 

    Removal of humic acid from aqueous solution using photocatalytic reaction on perlite granules covered by nano TiO2 particles

    , Article Journal of Molecular Liquids ; Volume 242 , 2017 , Pages 357-363 ; 01677322 (ISSN) Joolaei, H ; Vossoughi, M ; Rashidi Mehr Abadi, A ; Heravi, A ; Sharif University of Technology
    Humic acid (HA) constitutes a large portion of natural organic matter (NOM), and is the main precursor of toxic and cancerogenic Trihalomethanes compounds, formed during chlorination of drinking water. Therefore, it is essential that the humic acid be eliminated from water before treating it. The present study aims to investigate the photocatalytic degradation of humic acid (HA) using TiO2 nanoparticles immobilized on perlite granules (TIP), irradiated by UV light in a photoreactor. Samples of coated perlites were prepared by a dip coating method using a commercial powder of TiO2. Characteristics of the prepared samples were evaluated by X-ray and scanning electron microscope techniques.... 

    Linear spatial stability analysis of particle-laden stratified shear layers

    , Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 41, Issue 6 , 2019 ; 16785878 (ISSN) Khavasi, E ; Firoozabadi, B ; Sharif University of Technology
    Springer Verlag  2019
    Hydrodynamic instabilities at the interface of stratified shear layers could occur in various modes. These instabilities have an important role in the mixing process. In this work, the linear stability analysis in spatial framework is used to study the stability characteristics of a particle-laden stratified two-layer flow. The effect of parameters such as velocity-to-density thickness ratio, bed slope, viscosity as well as particle size on the stability is considered. A simple iterative method applying the pseudospectral collocation method that employed Chebyshev polynomials is used to solve two coupled eigenvalue equations. Based on the results, the flow becomes stable for Richardson... 

    Immobilization of penicillin G acylase on non-porous ultrafine silica particles

    , Article Scientia Iranica ; Volume 12, Issue 3 , 2005 , Pages 295-299 ; 10263098 (ISSN) Fazelinia, H ; Kheirolomoom, A ; Sharif University of Technology
    Sharif University of Technology  2005
    In this paper, immobilization of penicillin G aclylase onto non-porous ultrafine silica particles has been studied. The amount of penicillin G acylase immobilized was increased by increasing the free enzyme concentration and, at 0.45 mg/ml concentration of the free enzyme, 80% of the enzyme was immobilized. The optimum pH for immobilization was found to be 7.0, close to the pl of the enzyme. Although immobilization of the enzyme on ultrafine silica particles with and without glutaraldehyde showed almost the same activities, the enzyme immobilized with glutaraldehyde retained its initial activity much longer during 40 cycle-repeated batches with a half life of 163.2 h. © Sharif University of... 

    Investigation of particle dispersion and deposition in a channel with elliptic obstructions using lattice Boltzmann method

    , Article 2012 7th IEEE International Conference on Nano/Micro Engineered and Molecular Systems, NEMS 2012, 5 March 2012 through 8 March 2012 ; March , 2012 , Pages 523-528 ; 9781467311243 (ISBN) Tehrani, A ; Moosavi, A ; Sharif University of Technology
    Particle transport and deposition in a channel flow with elliptic obstruction is studied. Numerical simulation of fluid flow is performed using two-dimensional lattice Boltzmann method, while one-way coupling Lagrangian method for particle tracking is used. Standard particles are injected in the inlet of the channel. Gravity, Drag force, Brownian forces, and the Saffman lift are considered in equation of particle motion. The influence of geometrical parameter, ellipse aspect ratio, is studied on dispersion and deposition of particles as well as the flow parameters, such as Reynolds number. In addition, the effect of particles size -particles of 0.01-10μm in diameter- on dispersion and... 

    Simulation of 3D freely bubbling gas-solid fluidized beds using various drag models: TFM approach

    , Article Chemical Engineering Research and Design ; Volume 100 , 2015 , Pages 377-390 ; 02638762 (ISSN) Askaripour, H ; Molaei Dehkordi, A ; Sharif University of Technology
    Institution of Chemical Engineers  2015
    In this article, 3D modeling and simulation of bubbling fluidized beds has been conducted using various drag models, and the model predictions were validated against reported experimental data and 2D simulation results. In this regard, different drag models reported in the literature including Gidaspow, Syamlal-O'Brien, Hill-Koch-Ladd, and Wen-Yu were applied. A standard Two-Fluid Model (TFM) closed by the Kinetic Theory of Granular Flows (KTGF) was used to simulate bubbling gas-solid fluidized beds. Excellent agreements between the simulation results and experimental data, concerning bed expansion ratio, gas volume fraction, and time-averaged particles velocity, were found over a wide range... 

    Relative and interactive effects of fluid's physicochemical characteristics on the incipient motion of a granular particle under laminar flow condition

    , Article Journal of Hydraulic Engineering ; Volume 144, Issue 5 , 2018 ; 07339429 (ISSN) Xiao, M ; Gholizadeh Vayghan, A ; Adams, B. T ; Rajabipour, F ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2018
    This paper presents an experimental research for studying the relative and interactive effects of three physicochemical fluid characteristics (viscosity, pH, and ionic strength) on the incipient motion of a granular particle under laminar flow condition. Critical flow velocity for particle's incipient motion, an important factor for evaluating flow-induced soil erosion, was used to quantify the relative erosive capacity of the test fluids. Response surface methodology (RSM), a statistical design of experiments, was used to design and implement 20 test fluids with various levels of the three fluid characteristics. Incipient motion of a highly spherical glass bead positioned atop a specially... 

    Contribution of Iraqi and Syrian dust storms on particulate matter concentration during a dust storm episode in receptor cities: Case study of Tehran

    , Article Atmospheric Environment ; Volume 222 , 2020 Jalali Farahani, V ; Arhami, M ; Sharif University of Technology
    Elsevier Ltd  2020
    Frequent dust storms originated from Middle Eastern deserts impact major cities in Iran, including Tehran. Previous studies identified Iraqi and Syrian deserts as the main cross-border contributors to Tehran Particulate Matter (PM) levels. In this study, the contribution of Iraqi and Syrian dust storms to Tehran's PM10 and PM2.5 concentration were assessed during a dust storm episode. Initially, a dust storm event was identified through the statistical analysis of the recorded air pollution data at Tehran's monitoring stations and the visual inspection of the satellite images. A combination of CMAQ/WRF/SMOKE modeling systems was used to simulate PM concentrations from Tehran local sources... 

    An enhanced neural network model for predictive control of granule quality characteristics

    , Article Scientia Iranica ; Volume 18, Issue 3 E , 2011 , Pages 722-730 ; 10263098 (ISSN) Neshat, N ; Mahloojifl, H ; Kazemi, A ; Sharif University of Technology
    An integrated approach is presented for predicting granule particle size using Partial Correlation (PC) analysis and Artificial Neural Networks (ANNs). In this approach, the proposed model is an abstract form from the ANN model, which intends to reduce model complexity via reducing the dimension of the input set and consequently improving the generalization capability of the model. This study involves comparing the capability of the proposed model in predicting granule particle size with those obtained from ANN and Multi Linear Regression models, with respect to some indicators. The numerical results confirm the superiority of the proposed model over the others in the prediction of granule... 

    An intelligent approach for improved predictive control of spray drying process

    , Article INES 2010 - 14th International Conference on Intelligent Engineering Systems, Proceedings, 5 May 2010 through 7 May 2010, Las Palmas of Gran Canaria ; 2010 , Pages 127-136 ; 9781424476527 (ISBN) Azadeh, A ; Neshat, N ; Saberi, M ; Sharif University of Technology
    A flexible meta modelling approach is presented to predictive control of a drying process using Adaptive Neuro-Fuzzy Inference System (ANFIS), Artificial Neural Network (ANN) and Partial Least Squares (PLS) analysis. In the proposed approach, the PLS analysis is used to pre-process actual data and to provide the necessary background to apply ANN and ANFIS approaches. A reasonable section of this study is assigned to the modelling with aim at predicting the granule particle size and executing by ANFIS and ANN. ANN hold the promise of being capable of producing non-linear models, being able to work under noise conditions and being fault tolerant to the loss of neurons or connections. Also, the... 

    Black carbon and PM2.5 monitoring campaign on the roadside and residential urban background sites in the city of Tehran

    , Article Atmospheric Environment ; Volume 218 , 2019 ; 13522310 (ISSN) Taheri, A ; Aliasghari, P ; Hosseini, V ; Sharif University of Technology
    Elsevier Ltd  2019
    Fine particulate matter characterized as PM2.5 is the most important criteria air pollutant in the city of Tehran. Tehran is one of the most polluted cities of the Middle East based on annual mean PM2.5 concentrations. Tehran emission inventory shows the large contribution of mobile sources to the total particles. PM2.5 source apportionment studies show large fraction of black carbon (BC) in the total mass of PM2.5, especially during the cold seasons. BC is the product of incomplete combustion that is mainly derived from diesel engines and rich-burned gasoline carburetor engines on scooters and light-duty vehicles. The present study shows the results of a large experimental campaign in which... 

    A novel regression imputation framework for Tehran air pollution monitoring network using outputs from WRF and CAMx models

    , Article Atmospheric Environment ; Volume 187 , 2018 , Pages 24-33 ; 13522310 (ISSN) Shahbazi, H ; Karimi, S ; Hosseini, V ; Yazgi, D ; Torbatian, S ; Sharif University of Technology
    Elsevier Ltd  2018
    Missing or incomplete data in short or long intervals is a common problem in measuring air pollution. Severe issues may arise when dealing with missing data for time-series prediction schemes or mean analysis. This study aimed to develop a new regression imputation framework to impute missing values in the hourly air quality data set of Tehran and enhance the applicability of Tehran Air Pollution Forecasting System (TAPFS). The proposed framework was designed based on three types of features including measurements of other stations, WRF and CAMx physical models. In this framework, elastic net and neuro-fuzzy networks were efficiently combined in a two-layer structure. The framework was... 

    Short-term associations between daily mortality and ambient particulate matter, nitrogen dioxide, and the air quality index in a Middle Eastern megacity

    , Article Environmental Pollution ; Volume 254 , 2019 ; 02697491 (ISSN) Amini, H ; Trang Nhung, N. T ; Schindler, C ; Yunesian, M ; Hosseini, V ; Shamsipour, M ; Hassanvand, M. S ; Mohammadi, Y ; Farzadfar, F ; Vicedo Cabrera, A. M ; Schwartz, J ; Henderson, S. B ; Künzli, N ; Sharif University of Technology
    Elsevier Ltd  2019
    There is limited evidence for short-term association between mortality and ambient air pollution in the Middle East and no study has evaluated exposure windows of about a month prior to death. We investigated all-cause non-accidental daily mortality and its association with fine particulate matter (PM2.5), nitrogen dioxide (NO2), and the Air Quality Index (AQI) from March 2011 through March 2014 in the megacity of Tehran, Iran. Generalized additive quasi-Poisson models were used within a distributed lag linear modeling framework to estimate the cumulative effects of PM2.5, NO2, and the AQI up to a lag of 45 days. We further conducted multi-pollutant models and also stratified the analyses by... 

    Source apportionment of fine particulate matter in a Middle Eastern Metropolis, Tehran-Iran, using PMF with organic and inorganic markers

    , Article Science of the Total Environment ; Volume 705 , 2020 Esmaeilirad, S ; Lai, A ; Abbaszade, G ; Schnelle Kreis, J ; Zimmermann, R ; Uzu, G ; Daellenbach, K ; Canonaco, F ; Hassankhany, H ; Arhami, M ; Baltensperger, U ; Prévôt, A. S. H ; Schauer, J. J ; Jaffrezo, J. L ; Hosseini, V ; El Haddad, I ; Sharif University of Technology
    Elsevier B.V  2020
    With over 8 million inhabitants and 4 million motor vehicles on the streets, Tehran is one of the most crowded and polluted cities in the Middle East. Frequent exceedances of national daily PM2.5 limit have been reported in this city during the last decade, yet, the chemical composition and sources of fine particles are poorly determined. In the present study, 24-hour PM2.5 samples were collected at two urban sites during two separate campaigns, a one-year period from 2014 to 2015 and another three-month period at the beginning of 2017. Concentrations of organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals and specific organic molecular markers were measured by chemical...