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    Numerical investigation on the effect of the size and number of stages on the tesla microvalve efficiency

    , Article Journal of Mechanics ; Volume 29, Issue 3 , 2012 , Pages 527-534 ; 17277191 (ISSN) Mohammadzadeh, K ; Kolahdouz, E. M ; Shirani, E ; Shafii, M. B ; Sharif University of Technology
    In the present study, the effect of the number of stages of Tesla Micro-Valve (TMV), as well as the dependency of Reynolds number, Re, on the valve performance has been analyzed. For this purpose, different layouts include one to four-stage with different sizes are investigated numerically. The main criterion for evaluation of valves performance is diodicity, Di. Unsteady and steady flow in valve have been simulated and compared. It is shown that although there are some difference but the trend is similar for both responses. Finally, 2-D and steady state computations of the fluid flow have been utilized that reveal a strong dependence of Di on Re and pressure drop, ΔP. The results showed... 

    Sulfide stress corrosion cracking and hydrogen induced cracking of A216-WCC wellhead flow control valve body

    , Article Case Studies in Engineering Failure Analysis ; Volume 1, Issue 3 , 2013 , Pages 223-234 ; 22132902 (ISSN) Ziaei, S. M. R ; Kokabi, A. H ; Nasr Esfehani, M ; Sharif University of Technology
    The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran's sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. One failed valve body was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The valve body alloy was A216-WCC cast carbon steel. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results... 

    Numerical optimization of three-cavity magneto mercury reciprocating (MMR) micropump

    , Article Engineering Applications of Computational Fluid Mechanics ; Volume 15, Issue 1 , 2021 , Pages 1954-1966 ; 19942060 (ISSN) Mehrabi, A ; Mofakham, A. A ; Shafii, M. B ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    The operation of the three-cavity magneto mercury reciprocating (MMR) micropump, whose prototype were presented in an earlier companion paper, was numerically explored. In the three-cavity MMR micropump, three mercury slugs are moved by a periodic Lorentz force with a phase difference in three separate cavities. A consecutive motion of the slugs in their cavities transfer air from the inlet to the outlet. Two-dimensional OpenFOAM simulations were carried out to explore the influence of electric current excitation phase difference and back-pressure. The numerical simulations predicted the MMR micropump (with no valve) with a phase difference of (Formula presented.) and (Formula presented.)... 

    An experimental study of time lag for pressure measurement in different tubes

    , Article Amirkabir (Journal of Science and Technology) ; Volume 16, Issue 61 B , 2005 , Pages 127-137 ; 10150951 (ISSN) Mani, M ; Soltani, M. R ; Tolouei, E ; Sharif University of Technology
    Determination of the time lag caused by utilization of different tubes to measure pressure on the surface of a wind tunnel model is an important problem in the field of aerodynamic especially for unsteady measurements where the pressure signature changes continuously with time. In this investigation the time required for the applied pressure at one end of different tubes to reach its original value (applied pressure) at the other end has been measured. Three plastic tubes and two polyethylene tubes with different lengths and different inner diameters; L=2, 5 and 10 m, d=1, 2 and 4 mm, were used to study the time lag. Experimental data show that the response time in a pressure measuring... 

    Effects of polydimethylsiloxane grafting on the calcification, physical properties, and biocompatibility of polyurethane in a heart valve

    , Article Journal of Applied Polymer Science ; Volume 98, Issue 2 , 2005 , Pages 758-766 ; 00218995 (ISSN) Dabagh, M ; Abdekhodaie, M. J ; Khorasani, M. T ; Sharif University of Technology
    Segmented polyurethane (PU) has proven to be the best biomaterial for artificial heart valves, but the calcification of polyurethane surfaces causes serious problems in long-term implants. This work was undertaken to evaluate the effects of polydimethylsiloxane (PDMS) grafting on the calcification, biocompatibility, and blood compatibility of polyurethane. A grafted polyurethane film was compared with virgin polyurethane surfaces. Physical properties of the samples were examined using different techniques. The hydrophobicity of the polyurethane films increased as a result of silicone modification. The effects of surface modification of polyurethane films on their calcification and fibroblast... 

    Valve fault diagnosis in internal combustion engines using acoustic emission and artificial neural network

    , Article Shock and Vibration ; Vol. 2014 , 2014 ; ISSN: 10709622 Jafari, S. M ; Mehdigholi, H ; Behzad, M ; Sharif University of Technology
    This paper presents the potential of acoustic emission (AE) technique to detect valve damage in internal combustion engines. The cylinder head of a spark-ignited engine was used as the experimental setup. The effect of three types of valve damage (clearance, semicrack, and notch) on valve leakage was investigated. The experimental results showed that AE is an effective method to detect damage and the type of damagein valves in both of the time and frequency domains. An artificial neural network was trained based on time domain analysis using AE parametric features (AErms, count, absolute AE energy, maximum signal amplitude, and average signal level). The network consisted of five, six, and... 

    Failure analysis: Sulfide stress corrosion cracking and hydrogen-induced cracking of A216-WCC wellhead flow control valve body

    , Article Journal of Failure Analysis and Prevention ; Vol. 14, issue. 3 , 2014 , p. 376-383 Ziaei, S. M. R ; Kokabi A.H ; Mostowfi J ; Sharif University of Technology
    The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran's sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. One failed valve body was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The valve body alloy was A216-WCC cast carbon steel. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results... 

    Inhomogeneous swelling behavior of temperature sensitive PNIPAM hydrogels in micro-valves: Analytical and numerical study

    , Article Smart Materials and Structures ; Volume 24, Issue 4 , February , 2015 ; 09641726 (ISSN) Mazaheri, H ; Baghani, M ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
    Institute of Physics Publishing  2015
    In this work, inhomogeneous swelling of the temperature-sensitive PNIPAM hydrogel is investigated with application to micro-valves. In this regard, a modified model is considered, and an analytical solution of the inhomogeneous swelling of a hydrogel jacket coated on a rigid pillar is performed, which is valuable for the conceptual design of the micro-valve. Then, finite element implementation of the modified model is carried out, and its validity is verified by both the analytical and experimental results. Thereafter, thermo-mechanical behavior of the micro-valve is investigated considering the coupling between the inhomogeneous swelling of the jacket and contact problems due to the... 

    Design a Welding Robot for Repairing the Seat of Steam Control Valves of a Powerplant in Site

    , M.Sc. Thesis Sharif University of Technology Alemrajabi Firuzabad, Alireza (Author) ; Durali, Mohammad (Supervisor)
    Control valves of steam turbine of steam powerplant or the combined cycle are conected to the turbine's body and if there is any malfunction, it must be separated from turbine and after repairing, should be welded again to the body.This process needs enough time and high cost that’s why some well-known companies are repairing in the powerplant by design and making robots.Also using robots are made by well-known companies has high cost fees which can't justify it according to repair times.Thats why on the strangth of powerplant's authorities discussion (negotiation) design and making valve repaired robots which consists measurement, machining and welding is known as a project that repairs on... 

    A new model for dynamic analysis of side mounted diffuser valve micropumps

    , Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) Ahmadian, M. T ; Mehrabian, A ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Valveless micropumps are widely used due to simple structure, durability and low maintenance. Understanding the fluid-membrane interaction and performance criteria is still a challenging problem for the scientists. In this work, a new model for side mounted valve micropumps is developed to obtain dynamic response of micropump with respect to piezoelectric actuation. The parameters of this model are obtained in terms of actuation frequency and geometrical dimensions of the micropump. Balancing elastic, inertial and damping forces result in the governing equation of the micropump system model. Analytical studies for the bottom mounted valve micropump indicate pump flux is independent of the... 

    Analysis and optimized design of a packaged liquid chiller (part I -Analytical modelling)

    , Article 2005 ASME Summer Heat Transfer Conference, HT 2005, San Francisco, CA, 17 July 2005 through 22 July 2005 ; Volume 4 , 2005 , Pages 461-466 ; 0791847314 (ISBN); 9780791847312 (ISBN) Heydari, A ; Kargar, S ; Sharif University of Technology
    The purpose of this work is to develop a physical simulation model for the purpose of studying the effect of various design parameters on the performance of a packaged liquid chiller. A computer model which simulates the steady-state cyclic performance of a vapor compression chiller is developed for the purpose of performing detailed physical design analysis of actual industrial chillers. The model can be used for optimizing design and for detailed energy efficiency analysis of packaged liquid chillers. The simulation model takes into account presence of all chiller components such as compressor, shell-and-tube condenser and evaporator heat exchangers, thermostatic expansion valve and... 

    Optimization and Manufacturing Valve Seat Insert of Iron base Alloy for CNG Engines

    , M.Sc. Thesis Sharif University of Technology Hosseini, Abdolhamid (Author) ; Varhram, Naser (Supervisor)
    Regard to high temperature and using dry fuel in engines with CNG (Compressed Natural Gas), wear problems and instability of valve seat insert (VSI) in these types of engines have been increased. Today some of high alloy steel (consist of Cr,Ni,Co,W,Mo, . . .), Ni-base alloy or Co-base alloy are used in manufacturing VSI. It's clear these materials have high price. In powder metallurgy methods high percentage alloy is used for manufacturing VSI. These are the reasons why casting method for VSI manufacturing has been pleasant to be used.
    In this project the cast iron has been used for CNG engine VSI, by adding some elements like Mo,V,W, and Nb. The graphite has been used as solid... 

    Feasibility of using bulk metallic glass for self-expandable stent applications

    , Article Journal of Biomedical Materials Research - Part B Applied Biomaterials ; Volume 105, Issue 7 , 2017 , Pages 1874-1882 ; 15524973 (ISSN) Praveen Kumar, G ; Jafary Zadeh, M ; Tavakoli, R ; Cui, F ; Sharif University of Technology
    Self-expandable stents are widely used to restore blood flow in a diseased artery segment by keeping the artery open after angioplasty. Despite the prevalent use of conventional crystalline metallic alloys, for example, nitinol, to construct self-expandable stents, new biomaterials such as bulk metallic glasses (BMGs) are being actively pursued to improve stent performance. Here, we conducted a series of analyses including finite element analysis and molecular dynamics simulations to investigate the feasibility of using a prototypical Zr-based BMG for self-expandable stent applications. We model stent crimping of several designs for different percutaneous applications. Our results indicate... 

    Immobilization of functionalized gold nanoparticles in a well-organized silicon-based microextracting chip followed by online thermal desorption-gas chromatography

    , Article Microchemical Journal ; Volume 143 , 2018 , Pages 205-211 ; 0026265X (ISSN) Allahdadlalouni, M ; Bagheri, H ; Zamani, C ; Sharif University of Technology
    Elsevier Inc  2018
    In this survey, firstly, a silicon wafer-based microchip, possessing a 50-cm microchannel with the dimensions of 120 and 60 μm, was manufactured by chemical etching technique. Subsequently, the inner surface of the microchannel was coated with a primary layer of gold nanoparticles synthesized by galvanic displacement. Then a self-assembled monolayer of 3-mercaptopropyltriethoxysilane was immobilized on the first layer. Eventually, a polydimethylsiloxane film with a thickness of 16 ± 1 μm was formed on the walls of the microchannel by means of sol-gel method. Field emission scanning electron microscopy and atomic force microscopy were extensively employed to investigate the status of both... 

    A novel mathematical-heuristic method for non-convex dynamic economic dispatch

    , Article International Review of Electrical Engineering ; Volume 4, Issue 1 , 2009 , Pages 108-113 ; 18276660 (ISSN) Hosseini, H ; Salehi Dobakhshari, A ; Jalayer, R ; Sharif University of Technology
    Dynamic economic dispatch (DED) determines system generation schedule in a specified time interval to meet load demand at each hour while satisfying generation system constraints. DED considering valve-point effects is a non-convex optimization problem and therefore conventional mathematical methods fail to solve this problem. This paper presents a hybrid gradient search - near optimal search method to solve the DED problem considering valve-point effects of generating units. Local minima obtained by Gradient Search Method (GSM) are utilized by a novel Near Optimal Search (NOS) method to find the global optimum of the DED problem. The efficiency and feasibility of the proposed method and its... 

    Time-dependent analysis of leaflets in mechanical aortic bileaflet heart valves in closing phase using the finite strip method

    , Article Medical Engineering and Physics ; Volume 28, Issue 2 , 2006 , Pages 122-133 ; 13504533 (ISSN) Mohammadi, H ; Ahmadian, M. T ; Wan, W. K ; Sharif University of Technology
    Background and aims of the study: Mechanical heart valves (MHV) are widely used to replace dysfunctional and failed heart valves. The bileaflet MHV design is very popular due to its superior hemodynamics. Since their introduction in 1977, the hemodynamics of bileaflet prostheses has been extensively studied. In this study the dynamic behaviour during the closing phase of a bileaflet MHV under normal physiological conditions has been investigated. Methods: Fluid analysis is based on the control volume with moving boundaries in the vicinity of the occluder. Unsteady continuity equation, unsteady momentum equation on the control volume and unsteady Bernoulli's equation have been used to... 

    Monitoring of Valve Leakage in Internal Combustion Engine Using Acoustic Emission Method

    , Ph.D. Dissertation Sharif University of Technology Jafari, Mohammad (Author) ; Behzad, Mehdi (Supervisor) ; Mehdigholi, Hamid (Supervisor) ; Ahmadi, Mohammad Mehdi (Co-Advisor)
    Valve leak detection is very important due to bad direct effects on parts life and engine power. Acoustic emission (AE) has a good known ability on leak detection between fault detection methods. The aim of this thesis is presenting the ability of AE method for valve leak detection in internal combustion engines. The research method in a general framework based on the idea that firstly some evaluations were done in static tests for leakage due to three faults including clearance, quasi-crack and notch. Then, the evaluations were continued with dynamic analysis of rotational speeds and different loads on the engine. Finally, the neural network approach was used to automatically detect all... 

    Modeling and Sensitivity Analysis of a Sample Electro Hydraulic Servo Valve

    , M.Sc. Thesis Sharif University of Technology Nakhai, Amir Hassan (Author) ; Saadat Foumani, Mahmoud (Supervisor)
    Servo control valves including pressure control valves and flow control valves are the main components of the hydraulic system. Since these valves are responsible for controlling the flow or pressure in hydraulic systems, are important. In the present study, we focus on modeling and sensitivity analysis of an electro-servo-hydraulic valve with two stages. The first stage mechanism is the seating type (flapper-nozzle) and the second stage mechanism is the sliding type (spool type). For simulation main components of the servo valve include torque motor, flapper, flow through the nozzle-flapper, flow through the orifice and flow through the valve spool and body separately have been modeled.... 

    Imperialist competitive algorithm for solving non-convex dynamic economic power dispatch

    , Article Energy ; Volume 44, Issue 1 , 2012 , Pages 228-240 ; 03605442 (ISSN) Mohammadi Ivatloo, B ; Rabiee, A ; Soroudi, A ; Ehsan, M ; Sharif University of Technology
    Dynamic economic dispatch (DED) aims to schedule the committed generating units' output active power economically over a certain period of time, satisfying operating constraints and load demand in each interval. Valve-point effect, the ramp rate limits, prohibited operation zones (POZs), and transmission losses make the DED a complicated, non-linear constrained problem. Hence, in this paper, imperialist competitive algorithm (ICA) is proposed to solve such complicated problem. The feasibility of the proposed method is validated on five and ten units test system for a 24 h time interval. The results obtained by the ICA are compared with other techniques of the literature. These results... 

    A Second-Order Sliding Mode Observer for Fault Detection and Isolation of Turbocharged SI Engines

    , Article IEEE Transactions on Industrial Electronics ; Volume 62, Issue 12 , June , 2015 , Pages 7795-7803 ; 02780046 (ISSN) Salehi, R ; Vossoughi, G ; Alasty, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    This paper proposes a novel method for detection and isolation of wastegate (WG) faults in a turbocharged (TC) gasoline engine. This paper starts with a fault effect analysis on the WG faults, including WG stuck open and stuck closed, which is an early step in a detection strategy design. Then, a second-order sliding-mode observer (SOSMO) is proposed to capture the exhaust manifold dynamics. The observer uses experimentally validated engine models to estimate the WG position and a virtual force. The virtual force represents the external disturbances that disrupt the WG operation and enables the proposed SOSMO to estimate the WG position robust to the faults. Using this force, a detection and...