Search for: machinery
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    Improving productivity through increased capacity

    , Article World Cement ; Volume 34, Issue 7 , 2003 , Pages 99-105 ; 02636050 (ISSN) Safaieh, M. R ; Kakuei, A ; Sharif University of Technology
    The upgradation of the Kerman cement plant in Iran was discussed. It produces type 2,5 and pozzolanic cements which constitute almost 4.2% of the cement used in Iran. A short description of the process used, and some observations and recommendations about the plant were also provided  

    Application of sensitivity analysis to the development of high performance adaptive hydraulic engine mounts

    , Article Vehicle System Dynamics ; Volume 39, Issue 4 , 2003 , Pages 257-278 ; 00423114 (ISSN) Foumani, M. S ; Khajepour, A ; Durali, M ; Sharif University of Technology
    In this paper, the sensitivity analysis is applied to the development of high performance adaptive hydraulic mounts. The analysis allows us to select the most effective design parameters for tuning an adaptive mount to different road and engine conditions. It is shown that in the low frequency road excitation, the upper chamber compliance and inertia of the fluid column in the inertia track are the most influential properties in changing the dynamic stiffness of the hydraulic mount. These properties for the high frequency engine excitations are the upper compliance and the inertia of the fluid column of the decoupler. For tuning the adaptive mount to different road and engine excitation, a... 

    Design method and feasibility study of fully actively controlled frames

    , Article Scientia Iranica ; Volume 11, Issue 1-2 , 2004 , Pages 50-59 ; 10263098 (ISSN) Joghataie, A ; Asbmarz, M. M ; Sharif University of Technology
    Sharif University of Technology  2004
    In this paper, results of a preliminary study on the feasibility of using an Active Tendon Control (ATC) mechanism for frame structures subject to earthquakes is presented. So far, the ATC mechanism has mainly been considered as a means for installation on structures to mitigate their response under severe loading. In this study, it is desired to evaluate the possibility of using the ATC mechanism to serve as the main means for the stability of frames against earthquakes. Hence, a methodology is presented for the integrated design of frames with ATC mechanisms, which is tested numerically. A number of five-, ten-, fifteen- and twenty-story steel frames are used for this purpose. To this end,... 

    Time-frequency feature extraction of a cracked shaft using an adaptive kernel

    , Article 6th Internaional Conference on Modern Practice in Stree and Vibration Analysis, Bath, 5 September 2005 through 7 September 2005 ; Volume 5-6 , 2006 , Pages 37-44 ; 16609336 (ISSN); 0878494189 (ISBN); 9780878494187 (ISBN) Behzad, M ; Ghias, A. R ; Sharif University of Technology
    Trans Tech Publications Ltd  2006
    Adaptive time-frequency representations have many advantages compared with conventional methods. In this paper, a new method is proposed to adapt Smoothed Pseudo WignerVille distribution to match signal's time-frequency content. It is based on maximizing a local time-frequency concentration measure for different time and frequency smoothing window lengths. Subsequently, the optimized values are used for constructing an adaptive kernel over time. The proposed transform is then applied to vibration signals of healthy and cracked shafts which are acquired through run-up, and the crack signature is obtained. Results show that enhanced improvement in resolution is obtained while the computational... 

    Evaluation of imperial performance characteristic of turbocharger turbine and compressor

    , Article 9th AIAA/ASME Joint Thermophysics and Heat Transfer Conference Proceedings, San Francisco, CA, 5 June 2006 through 8 June 2006 ; Volume 2 , 2006 , Pages 1019-1028 ; 1563478153 (ISBN); 9781563478154 (ISBN) Rad, M ; Hajilouy, A ; Shahhosseini, M. R ; Sharif University of Technology
    Performance characteristics of turbocharger turbine and compressor such as efficiency, mass parameter and power are determined experimentally at turbocharger laboratory. Accurate determination of the performance map is significant for manufacturers as well as end users. To this end accurate measurement of test parameters such as temperature, pressure, and speed are required. In this paper an analytic method to predict the measurement uncertainties in turbocharger laboratory, is described. Furthermore the effect of each test parameter on the performance uncertainty is considered. Test parameters that have the most significant influence on the performance uncertainties are identified.... 

    Effect of centrifugal force on natural frequency of lateral vibration of rotating shafts

    , Article Journal of Sound and Vibration ; Volume 274, Issue 3-5 , 2004 , Pages 985-995 ; 0022460X (ISSN) Behzad, M ; Bastami, A. R ; Sharif University of Technology
    Academic Press  2004
    This paper investigates the effect of shaft rotation on its natural frequency. Apart from gyroscopic effect, the axial force originated from centrifugal force and the Poisson effect results in change of shaft natural frequency. D'Alembert principle for shaft in cylindrical co-ordinate system, along with the stress-strain relation, gives the non-homogenous linear differential equation, which can be used to calculate axial stress in the shaft. Numerical results of this study show that axial stress produced by shaft rotation has a major effect on the natural frequency of long high-speed shafts, while shaft diameter has no influence on the results. In addition, change in lateral natural... 

    Effect of motor speed on the optimum operating point of direct torque controlled induction motor

    , Article 6th International Conference on Electrical Machines and Systems, ICEMS 2003, 9 November 2003 through 11 November 2003 ; Volume 2 , 2003 , Pages 619-622 ; 750626210X (ISBN); 9787506262101 (ISBN) Kaboli, S ; Zolghadri, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    The flux and torque hysteresis bands are the only gains to be adjusted in direct torque control (DTC). The torque ripple and harmonic loss of motor and switching loss of inverter are greatly influenced by them. In this paper the effects of flux and torque hysteresis bands on inverter switching loss, harmonic loss and torque ripple of induction motor are investigated through a cost function. Minimizing this cost function leads to the optimum value of the hysteresis bands of torque and flux controllers. The effect of motor speed on cost function is also investigated. © 2003 International Academic Publishers/World Publishing Corporation  

    Small-scale oriented elasticity modeling of functionally graded rotating micro-disks with varying angular velocity in the context of the strain gradient theory

    , Article Acta Mechanica ; Volume 232, Issue 6 , 2021 , Pages 2395-2416 ; 00015970 (ISSN) Bagheri, E ; Asghari, M ; Kargarzadeh, A ; Badiee, M ; Sharif University of Technology
    Springer  2021
    During the varying angular speed timespans of the start or shutdown of rotating machinery, the machinery components may be subjected to intense mechanical loadings which should be taken into account by its fabricator in the designing processes. In the microscale rotating systems, where the angular velocity is typically very high, the importance of this issue is much higher. In this paper, a comprehensive strain-gradient elasticity formulation is presented for functionally graded rotating micro-disks under the effects of varying angular velocity. The gradation of the constituent material along the radial direction can be a helpful option to mitigate the stresses in rotating micro-disks under... 

    Political Conflicts, Uncertainty and Investment in Iran

    , M.Sc. Thesis Sharif University of Technology Habibpour Moghaddam, Ehsan (Author) ; Barakchian, Mahdi (Supervisor) ; Nili, Masoud (Co-Supervisor)
    Investment is a variable that would determine the future status of the economy. Given the fact that the investment behavior consequences in the economy would appear in the long-term horizons, unlike most other state variables, such as inflation and exchange rates, it may not be a tangible variable. As a result, there may be fewer sensitivities toward it. However, looking at the evidence, it is observable that the level of investment in Iran has experienced a severe reduction since the early 2010s, and this decline in investment has remained stable in its trend. The real aggregate investment level in Iran at the end of the year 2018 was approximately equal to its level in the year 2002. There... 

    An analytical approach in analysis of local oscillator near-the-carrier AM noise suppression in microwave balanced mixers

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 57, Issue 4 , 2009 , Pages 760-766 ; 00189480 (ISSN) Kheirdoost, A ; Banai, A ; Farzaneh, F ; Sharif University of Technology
    In this paper, a new formulation based on conversion matrix method is proposed to analyze near-the-carrier local ocillator (LO) noise down conversion to IF in microwave mixers. This method could be easily applied to analyze LO noise down conversion in any type of mixer. Practical results of this method have been compared with the envelope method and measurement results. It is shown that despite the conventional AM noise suppression in balanced mixers, the near-the-carrier LO noise suppression does not occur necessarily at the center frequency of hybrid in balanced mixers. AM noise suppression values are predicted precisely. © 2006 IEEE  

    Modeling and simulation of desiccant wheel for air conditioning

    , Article Energy and Buildings ; Volume 38, Issue 10 , 2006 , Pages 1230-1239 ; 03787788 (ISSN) Esfandiari Nia, F ; van Paassen, D ; Saidi, M. H ; Sharif University of Technology
    This paper presents the modeling of a desiccant wheel used for dehumidifying the ventilation air of an air-conditioning system. The simulation of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out with MATLAB Simulink. Using the numerical method, the performance of an adiabatic rotary dehumidifier is parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. The solutions of the simulation at different conditions used in air dehumidifier have been investigated according to the previous published studies. The model is validated through comparison the simulated results with... 

    Uncontrolled disorder effects in fabricating photonic quantum simulators on a kagome geometry: A projected-entangled-pair-state versus exact- diagonalization analysis

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Vol. 89, Issue. 6 , 2014 ; ISSN: 10502947 Hosseinkhani, A ; Dezfouli, B. G ; Ghasemipour, F ; Rezakhani, A. T ; Saberi, H ; Sharif University of Technology
    We propose a flexible numerical framework for extracting the energy spectra and photon transfer dynamics of a unit kagome cell with disordered cavity-cavity couplings under realistic experimental conditions. A projected-entangled pair state (PEPS) Ansatz to the many-photon wave function allows us to gain a detailed understanding of the effects of undesirable disorder in fabricating well-controlled and scalable photonic quantum simulators. The correlation functions associated with the propagation of two-photon excitations reveal intriguing interference patterns peculiar to the kagome geometry and promise at the same time a highly tunable quantum interferometry device with a signature for the... 

    Modeling active micromixers with multiple microstirrers using smoothed particle hydrodynamics

    , Article Scientia Iranica ; Vol. 21, issue. 4 , 2014 , pp. 1390-1402 ; ISSN: 10263098 Jafarian, A ; Pishevar, A ; Saidi, M. S ; Sharif University of Technology
    The smoothed particle hydrodynamics method is used to explore the effects of design parameters on the mixing efficiency of two types of active micromixer. First, the complex flow field and the mixing process of two separated fluids in a square mixing chamber with nine symmetric microstirrers are simulated. The influence of design parameters, such as the microstirrer rotation arrangement and the angular velocity of the microstirrer, on the mixing performance, is investigated. The mixing index parameter on ten control points is calculated and the average mixing index is compared for different cases. Simulations illustrate that the rotation arrangement of microstirrers is a key parameter in the... 

    Stochastic scheduling with minimizing the number of tardy jobs using chance constrained programming

    , Article Mathematical and Computer Modelling ; Volume 57, Issue 5-6 , 2013 , Pages 1154-1164 ; 08957177 (ISSN) Elyasi, A ; Salmasi, N ; Sharif University of Technology
    In this research, two scheduling problems i.e., single machine scheduling problem with minimizing the number of tardy jobs (1∥∑Uj) and two machine flow shop scheduling problem with a common due date and minimizing the number of tardy jobs (F2{pipe}dj=d{pipe}∑Uj) are investigated in a stochastic setting in the class of non-preemptive static list policies. It is assumed that the processing times of jobs are independent random variables. The stochastic problems are solved based on chance constrained programming. An equivalent deterministic problem is generated for each stochastic problem by linearization of the chance constraints. Then, the generated deterministic problems are solved using... 

    Slipping and rolling on an inclined plane

    , Article European Journal of Physics ; Volume 32, Issue 4 , 2011 , Pages 1049-1057 ; 01430807 (ISSN) Aghamohammadi, C ; Aghamohammadi, A ; Sharif University of Technology
    In the first part of the paper, using a direct calculation two-dimensional motion of a particle sliding on an inclined plane is investigated for general values of friction coefficient (μ). A parametric equation for the trajectory of the particle is also obtained. In the second part of the paper, the motion of a sphere on the inclined plane is studied. It is shown that the evolution equation for the contact point of a sliding sphere is similar to that of a point particle sliding on an inclined plane whose friction coefficient is 7/2 μ. If μ > 2/7 tanθ, for any arbitrary initial velocity and angular velocity, the sphere will roll on the inclined plane after some finite time. In other cases, it... 

    Detail study on improving micro/nano gas mixer performances in slip and transitional flow regimes

    , Article Sensors and Actuators, B: Chemical ; Volume 218 , October , 2015 , Pages 78-88 ; 09254005 (ISSN) Darbandi, M ; Sabouri, M ; Sharif University of Technology
    Elsevier  2015
    The mixer geometry has substantial effect on mixing performance of different micro/nanomixers. Despite past numerous studies dedicated to mixing of liquid flow streams, there are less efforts to investigate the geometry effects on gas mixing performances. In this work, we focus on gas-gas mixing through different micro/nanoscale mixers under slip and transitional flow regimes. We use the direct simulation Monte Carlo (DSMC) method to provide accurate and reliable results in such flow regimes. To extend our study, we implement different geometrical parameters in our consideration including the mixer size, the impact angle between two incoming gas streams, and the contraction height located in... 

    Vibration absorber design to suppress regenerative chatter in nonlinear milling process: Application for machining of cantilever plates

    , Article Applied Mathematical Modelling ; Volume 39, Issue 2 , 2015 , Pages 600-620 ; 0307904X (ISSN) Moradi, H ; Vossoughi, G ; Behzad, M ; Movahhedy, M. R ; Sharif University of Technology
    Elsevier Inc  2015
    In this paper, a tunable vibration absorber (TVA) is designed to suppress regenerative chatter in milling of cantilever plates. In machining industry, the majority of work-piece materials or the interaction of work-piece/cutting tool causes the cutting forces to demonstrate nonlinear behavior. The application of TVA (as a semi-active controller) is investigated for the process with an extensive nonlinear model of cutting forces. Under regenerative chatter conditions, optimum values of the absorber position and its spring stiffness are found such that the plate vibration is minimized. For this purpose, an optimal algorithm is developed based on mode summation approach. Results are presented... 

    A non-linear model for the classification of stored items in supply chain management

    , Article Proceedings 2010 International Symposium on Information Technology - System Development and Application and Knowledge Society, ITSim'10, 15 June 2010 through 17 June 2010 ; Volume 3 , June , 2010 , Pages 1636-1641 ; 9781424467181 (ISBN) Bozorgi Rad, S.Y ; Bozorgi Rad, M. A ; Ishak Desa, M ; Behnam, S ; Lessanibahri, S ; IEEE ; Sharif University of Technology
    With the significant role that warehouse plays in connection to suppliers, distributors, and clients, and considering the costliness of storage systems, efforts have focused on the reduction of procedural expenses. Among the most significant expenses, one involves the distance traveled by operators or S/R machinery for the selection of ordered items; the common solution to which has been through the classification of stored items. Previous articles have focused on linear solutions to the abovementioned problem, such as P-Median. This article shall focus on the problems arising from the said solution, and instead a non-linear method proposed. Further, a heuristic algorithm is produced for the... 

    Analyzing mixing quality in a curved centrifugal micromixer through numerical simulation

    , Article Chemical Engineering and Processing: Process Intensification ; 2017 ; 02552701 (ISSN) Shamloo, A ; Vatankhah, P ; Akbari, A ; Sharif University of Technology
    Elsevier B.V 
    The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over... 

    Mixing performance of T, Y, and oriented Y-micromixers with spatially arranged outlet channel: evaluation with villermaux/dushman test reaction

    , Article Microsystem Technologies ; 2016 , Pages 1-14 ; 09467076 (ISSN) Rahimi, M ; Azimi, N ; Parsamogadam, M. A ; Rahimi, A ; Masahy, M. M ; Sharif University of Technology
    Springer Verlag  2016
    This study aims to investigate the micromixing performance of three basic types of spatial shaped micromixers. New configurations of T, Y, and oriented Y-spatial mixers were designed with change in the angles of the confluence and the outlet channel to achieve the efficient micromixing. These micromixers offer advantages that are not attainable with the typical types of these mixers. Experimental tests were carried out in the laminar flow regime and the mixing efficiency was evaluated using Villermaux/Dushman test reaction. The geometries of the channels were cylindrical with the length of 30 mm and the diameter of 800 μm. The experimental results show that the angle of outlet channel has a...