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Total 838 records

    A new biomechanical method for objective measurement of spasticity: A preliminary study

    , Article International Journal of Therapy and Rehabilitation ; Volume 14, Issue 2 , 2007 , Pages 63-69 ; 17411645 (ISSN) Nakhostin Ansari, N ; Karimi, H ; Farahmand, F ; Naghdi, S ; Faghihzadeh, S ; Sharif University of Technology
    MA Healthcare Ltd  2007
    Abstract
    The assessment of the various impairments in brain damage including spasticity is important. The purpose of this study was to develop a new biomechanical method based on quantification of velocity reduction (VR) suitable for clinical use  

    Numerical study of diodicity mechanism in different tesla-type microvalves

    , Article Journal of Applied Research and Technology ; Volume 11, Issue 6 , 2013 , Pages 876-885 ; 16656423 (ISSN) Nobakht, A. Y ; Shahsavan, M ; Paykani, A ; Sharif University of Technology
    2013
    Abstract
    Microvalve is one of the most important components in microfluidic systems and micropumps. In this paper, threedimensional incompressible flow through a Tesla-type microvalve is simulated using FLUENT computational fluid dynamic package. The flow is laminar and SIMPLE algorithm is used. The second-order upwind method is implemented for discretizing convective terms. The diodicity mechanism is investigated in detail for three different microvalves. Effect of several series Tesla-type microvalves on diodicity is also studied. The numerical analyses reveal that the mechanism of diodicity occurs at the T-junction and side channel. If inlet and outlet channels are eliminated, diodicity can be... 

    Peculiar velocity measurement in a clumpy universe

    , Article International Journal of Modern Physics D ; 2017 ; 02182718 (ISSN) Habibi, F ; Baghram, S ; Tavasoli, S ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2017
    Abstract
    In this work, we address the issue of peculiar velocity measurement in a perturbed Friedmann universe using the deviations from measured luminosity distances of standard candles from background FRW universe. We want to show and quantify the statement that in intermediate redshifts ((Formula presented.)), deviations from the background FRW model are not uniquely governed by peculiar velocities. Luminosity distances are modified by gravitational lensing. We also want to indicate the importance of relativistic calculations for peculiar velocity measurement at all redshifts. Methods: For this task, we discuss the relativistic correction on luminosity distance and redshift measurement and show... 

    Peculiar velocity measurement in a clumpy universe

    , Article International Journal of Modern Physics D ; Volume 27, Issue 3 , 2018 ; 02182718 (ISSN) Habibi, F ; Baghram, S ; Tavasoli, S ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2018
    Abstract
    Aims: In this work, we address the issue of peculiar velocity measurement in a perturbed Friedmann universe using the deviations from measured luminosity distances of standard candles from background FRW universe. We want to show and quantify the statement that in intermediate redshifts (0.5 < z < 2), deviations from the background FRW model are not uniquely governed by peculiar velocities. Luminosity distances are modified by gravitational lensing. We also want to indicate the importance of relativistic calculations for peculiar velocity measurement at all redshifts. Methods: For this task, we discuss the relativistic correction on luminosity distance and redshift measurement and show the... 

    Slip velocity in pulsed disc and doughnut extraction columns

    , Article Chemical Industry and Chemical Engineering Quarterly ; Volume 17, Issue 3 , 2011 , Pages 333-339 ; 14519372 (ISSN) Torab Mostaedi, M ; Jalilvand, H ; Outokesh, M ; Sharif University of Technology
    2011
    Abstract
    In the present work, slip velocity has been measured in a 76 mm diameter pulsed disc and doughnut extraction column for four different liquid-liquid systems. The effects of operating variables including pulsation intensity and dispersed and continuous phase flow rates on slip velocity have been investigated. The existence of three different operational regimes, namely mixersettler, transition, and emulsion regimes, was observed when the energy input was changed. Empirical correlations are derived for prediction of the slip velocity in terms of operating variables, physical properties of the liquid systems, and column geometry for different regimes. Good agreement between prediction and... 

    Long-lived and unstable modes of Brownian suspensions in microchannels

    , Article Journal of Fluid Mechanics ; Volume 701 , 2012 , Pages 407-418 ; 00221120 (ISSN) Khoshnood, A ; Jalali, M. A ; Sharif University of Technology
    2012
    Abstract
    We investigate the stability of the pressure-driven, low-Reynolds-number flow of Brownian suspensions with spherical particles in microchannels. We find two general families of stable/unstable modes: (i) degenerate modes with symmetric and antisymmetric patterns; (ii) single modes that are either symmetric or antisymmetric. The concentration profiles of degenerate modes have strong peaks near the channel walls, while single modes diminish there. Once excited, both families would be detectable through high-speed imaging. We find that unstable modes occur in concentrated suspensions whose velocity profiles are sufficiently flattened near the channel centreline. The patterns of growing unstable... 

    Electronic features of rippled graphene

    , Article ICEE 2012 - 20th Iranian Conference on Electrical Engineering ; 2012 , Pages 170-172 ; 9781467311489 (ISBN) Haji Nasiri, S ; Moravvej Farshi, M. K ; Faez, R ; Bajelan, A ; Sharif University of Technology
    2012
    Abstract
    Using tight binding theory the effect of topological ripples on the electronic band structure, density of states (DOS), and Fermi velocity of graphene are studied. The results show that by an increase in the ripple height the graphene Fermi velocity decreases and its DOS increases.- Moreover, we show that an increase in the ripple period causes the graphene band gap and DOS to decrease and its Fermi velocity to increase  

    Experimental investigation of slip velocity and settling distribution of micro-particles in converging–diverging microchannel

    , Article Microsystem Technologies ; 2016 , Pages 1-10 ; 09467076 (ISSN) Shirinzadeh, F ; Saidi, M. H ; Davari, A ; Sharif University of Technology
    Springer Verlag  2016
    Abstract
    An experimental test bed based on single particle tracking techniques is employed in order to investigate the velocity domain, slip velocity, and settling distribution of micro-particles in low-Reynolds number poiseuille flow in converging–diverging microchannel. Three-dimensional velocity domain of particles are studied in the presence of walls and compared with the particle-free fluid. The results show that the velocity of particles moving near the side walls of microchannel decreases about 30 % compared to those moving at the centerline. Furthermore, the effects of converging–diverging geometry on sedimentation of micro-particles are considered. The results show an average decrease of... 

    Experimental investigation of slip velocity and settling distribution of micro-particles in converging–diverging microchannel

    , Article Microsystem Technologies ; Volume 23, Issue 8 , 2017 , Pages 3361-3370 ; 09467076 (ISSN) Shirinzadeh, F ; Saidi, M. H ; Davari, A ; Sharif University of Technology
    Springer Verlag  2017
    Abstract
    An experimental test bed based on single particle tracking techniques is employed in order to investigate the velocity domain, slip velocity, and settling distribution of micro-particles in low-Reynolds number poiseuille flow in converging–diverging microchannel. Three-dimensional velocity domain of particles are studied in the presence of walls and compared with the particle-free fluid. The results show that the velocity of particles moving near the side walls of microchannel decreases about 30 % compared to those moving at the centerline. Furthermore, the effects of converging–diverging geometry on sedimentation of micro-particles are considered. The results show an average decrease of... 

    A study on the computation of the redundant deformation factor in wire drawing of austenitic 304 stainless steel

    , Article Journal of Materials Processing Technology ; Volume 199, Issue 1 , 2008 , Pages 230-233 ; 09240136 (ISSN) Kazeminezhad, M ; Sharif University of Technology
    2008
    Abstract
    A study on the redundant deformation factor in wire drawing process of an austenitic 304 stainless steel is carried out. Utilizing the upper bound methods based on the trapezoidal and spherical velocity fields, the redundant deformation factors in different deformation conditions are calculated and the achieved results are compared with the results of the FEM and superposition method presented by other researchers. From the results it is concluded that when Δ values are lower than 5, the redundant deformation factors calculated from the spherical and trapezoidal velocity fields with angle β of 80-90° are valid. Also, the results of the trapezoidal velocity field with angle β of 90° are the... 

    Impact of middle eastern dust sources on PM10 in iran: highlighting the impact of tigris-euphrates basin sources and lake urmia desiccation

    , Article Journal of Geophysical Research: Atmospheres ; Volume 121, Issue 23 , 2016 , Pages 14,018-14,034 ; 2169897X (ISSN) Sotoudeheian, S ; Salim, R ; Arhami, M ; Sharif University of Technology
    Blackwell Publishing Ltd  2016
    Abstract
    Contribution of different Middle Eastern dust origins to PM10 (PM with aerodynamic diameters less than 10 µm) levels in several receptor large cities in Iran was investigated. Initially, the major regional dust episodes were determined through statistical analysis of recorded PM levels at air quality stations and verified using satellite images. The particles dispersion was simulated by Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) to regenerate PM10 during the dust episodes. The accuracy of the modeled results was rather convincing, with an average squared correlation coefficient (R2) of 0.7 (max = 0.95). Consequently, the contributions of different dust sources to the... 

    Experimental investigation of single walue variables of three-dimensional density current

    , Article Canadian Journal of Physics ; Volume 87, Issue 2 , 2009 , Pages 125-134 ; 00084204 (ISSN) Firoozabadi, B ; Afshin, H ; Shelkhi, J ; Sharif University of Technology
    2009
    Abstract
    The height of a dense layer underflow is defined as the interface between a dyed saline solution fluid and colorless ambient fluid. In this paper, the density current height or vision height of three-dimensional saline water under pure water is measured empirically, and the relation of this parameter with the location of maximum velocity is investigated. Because of the absence of a clear interface between the dense underflow and pure water, researchers were unable to define a unique parameter for the evaluation of density current height. The parameters used by some researchers include the height corresponding to the location of maximum, half-maximum, and quarter-maximum velocity in the... 

    A combined upper bound and finite element model for prediction of velocity and temperature fields during hot rolling process

    , Article International Journal of Mechanical Sciences ; Volume 50, Issue 9 , 2008 , Pages 1423-1431 ; 00207403 (ISSN) Serajzadeh, S ; Mahmoodkhani, Y ; Sharif University of Technology
    Elsevier Ltd  2008
    Abstract
    In this work, velocity field and temperature distribution during hot strip rolling are predicted, employing a combined upper bound and finite element analysis. At first, a velocity field is proposed utilizing the principle of volume constancy, and then the velocity field is modified by means of upper bound theorem. At the same time, a thermal-finite element analysis is utilized to determine temperature distribution within the metal as well as to calculate the flow stress of deforming material. The model is capable of considering the effects of different factors on temperature and velocity distributions such as rolling speed and interface heat transfer coefficient. In order to verify the... 

    Three dimensional numerical simulation of air flow over domed roofs

    , Article NUMERICAL ANALYSIS AND APPLIED MATHEMATICS: International Conference on Numerical Analysis and Applied Mathematics, Corfu, 16 September 2007 through 20 September 2007 ; Volume 936 , 2007 , Pages 191-194 ; 0094243X (ISSN) ; 073540447X (ISBN); 9780735404472 (ISBN) Faghih Khorasani, A. R ; Bahadori, M. N ; Sharif University of Technology
    2007
    Abstract
    Using domed roofs to reduce building solar load in hot arid area is one of Iranian mechanical engineering masterworks. The first application of these roofs was to cover large buildings such as mosques, shrines, etc. However their thermal performance made them to be employed in other buildings like bazaars. The aim of this study was to determine the air pressure and velocity distribution over domed roofs, by employing numerical methods. The results of this study will be used as the first step for thermal performance evaluation of domed roofs. © 2007 American Institute of Physics  

    Numerical investigation of transient thermo-fluid processes in a Ranque-Hilsch vortex tube

    , Article International Journal of Refrigeration ; Volume 131 , 2021 , Pages 746-755 ; 01407007 (ISSN) Mirjalili, M ; Ghorbanian, K ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    A 2D numerical investigation is performed to better understand the transient thermo-fluid processes in a vortex tube for a cold mass fraction equal to0.44. The results along the Ranque-Hilsch vortex tube reveal a close agreement with past numerical and experimental data. The distribution of axial, radial, and tangential velocities as well as the stagnation pressure and temperature are examined at different positions for different time steps. The results indicate that the tangential velocity is the most significant velocity component and dominates the heat transfer and energy conversion processes. In addition, it is evident that the core of the cold end experiences the highest pressure... 

    Numerical-Experimental geometric optimization of the Ahmed body and analyzing boundary layer profiles

    , Article Journal of Optimization Theory and Applications ; 2021 ; 00223239 (ISSN) Abdolmaleki, M ; Mashhadian, A ; Amiri, S ; Esfahanian, V ; Afshin, H ; Sharif University of Technology
    Springer  2021
    Abstract
    The trade-off between the fuel consumption and drag coefficient makes the investigations of drag reduction of utmost importance. In this paper, the rear-end shape optimization of Ahmed body is performed. Before changing the geometry, to identify the suitable simulation method and validate it, the standard Ahmed body is simulated using k − ω shear stress transport (SST) and k-epsilon turbulence models. The slant angle, rear box angle, and rear box length as variables were optimized simultaneously. Optimizations conducted by genetic algorithm (GA) and particle swarm optimization (PSO) methods indicate a 26.3% decrease in the drag coefficient. To ensure the validity of the results, a... 

    Numerical-Experimental geometric optimization of the ahmed body and analyzing boundary layer profiles

    , Article Journal of Optimization Theory and Applications ; 2021 ; 00223239 (ISSN) Abdolmaleki, M ; Mashhadian, A ; Amiri, S ; Esfahanian, V ; Afshin, H ; Sharif University of Technology
    Springer  2021
    Abstract
    The trade-off between the fuel consumption and drag coefficient makes the investigations of drag reduction of utmost importance. In this paper, the rear-end shape optimization of Ahmed body is performed. Before changing the geometry, to identify the suitable simulation method and validate it, the standard Ahmed body is simulated using k − ω shear stress transport (SST) and k-epsilon turbulence models. The slant angle, rear box angle, and rear box length as variables were optimized simultaneously. Optimizations conducted by genetic algorithm (GA) and particle swarm optimization (PSO) methods indicate a 26.3% decrease in the drag coefficient. To ensure the validity of the results, a... 

    Airflow in buildings with courtyards

    , Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 29, Issue 2 , 2005 , Pages 187-206 ; 03601307 (ISSN) Safarzadeh, H ; Bahadori, M. N ; Sharif University of Technology
    2005
    Abstract
    The airflow rate through a two-story building with a courtyard, with and without trees, was estimated and compared with that of a building without a courtyard. The building and the courtyard were of square shapes, each 10 m to the side. The courtyard walls were 3m high and two separate trees of spherical, cylindrical and conical shapes were considered in the yard. The courtyard was directly south of the building and a wind angle of zero degree was considered when the wind was blowing directly from the south. It was found that when the wind angles were between 0 to ±90 degrees, the airflow rate through the building was reduced when compared with the building without a courtyard. The presence... 

    Effect of up flow velocity and temperature on the performance of UASB system treating slaughtery effluent

    , Article World Water and Environmental Resources Congress 2001, Orlando, FL, 20 May 2001 through 24 May 2001 ; Volume 111 , 2004 ; 0784405697 (ISBN); 9780784405697 (ISBN) Torkian, A ; Hashemian, S. J ; Eqbali, A ; Sharif University of Technology
    2004
    Abstract
    Temperature and up flow velocity are regarded as the two main parameters significantly affecting microbial ecology and characteristics of UASB systems. The 2.3 m high and 0.25 m2-cross-section UASB pilot used in this study received slaughtery effluent with SCOD in the range of 2000-5000 mg/L. Temperature was varied in the 28-35 °C mesophilic range using an in-line heat exchanger and three up flow velocities studied were 0.3, 0.57, and 1 m/h without any recycling. At least one-week adjustment time was allowed after any change in the conditions. Since granules had been formed previously, the start-up phase lasted for only two weeks and up flow velocity and temperature was maintained at 0.3 m/h... 

    Flow field study over the wing of a fighter-type aircraft model

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 17, Issue 4 , 2004 , Pages 399-410 ; 1728-144X (ISSN) Soltani, M. R ; Khadivi, T ; Abbasi Hoseini, A ; Sharif University of Technology
    Materials and Energy Research Center  2004
    Abstract
    An extensive experimental investigation to study the flow structure over the wing of a fighter type configuration model has been conducted. The model used for this study was similar to the High Alpha Research Vehicle (HARV) that has been used in various European research centers for studying its force and moment characteristics. Tests were conducted at two subsonic speeds and at low to moderate angle of attack. The wing surface pressure distribution and velocity profiles at various angles of attack were measured. This investigation also included suction effects on the wing surface pressure signature. Smoke and tufts were used to visualize the flow over the wing. The results indicate...