Search for: transducers
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    Guard-ring effects on capacitive transducer systems

    , Article Scientia Iranica ; Volume 7, Issue 1 , 2000 , Pages 25-31 ; 10263098 (ISSN) Golnabi, H ; Sharif University of Technology
    Sharif University of Technology  2000
    In this paper, implementing a guard-ring electrode in a capacitive transducer system is described. The performance of the transducers with and without a guard-ring in terms of output linearity and dynamic range is investigated and deviations from the expected theoretical results are reported. The two-terminal capacitors perform well only for a small gap distance in the range of 2-3 mm while the three-terminal sensor (50 mm diameter) demonstrates a very good performance for a wide range of 0.5-5 mm. For a gap distance of 3 mm, the slope deviation for the sensors without a guard-ring is in the range of 15%-29%, whereas for the system with a guard-ring is only 6%, which clearly shows the range... 

    Measuring small displacements by using a capacitive transducer system

    , Article Scientia Iranica ; Volume 7, Issue 1 , 2000 , Pages 69-74 ; 10263098 (ISSN) Golnabi, H ; Sharif University of Technology
    Sharif University of Technology  2000
    In this paper, application of a capacitive sensor system in recording small displacements is discussed. Through using a simple transducer and a monitoring circuit, change in capacitance has been detected as a function of the capacitor air-gap distance. There is a linear relation between gap distance and output of a sensor for a wide gap range of 0.5 to 5 mm. The reported system provides means for measuring displacements up to 5 mm with a resolution better than 250 nm. By decreasing the dynamic range of the transducer to 250 μm, a small displacement of the order of 100 nm is detectable. With the present system, a minimum displacement of about 200 nm (200 ppm) for the gap distance of 1 mm is... 

    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... 

    Image quality equations for focused transducer in circular photoacoustic computed tomography

    , Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 917-921 ; 9781665433655 (ISBN) Hakakzadeh, S ; Kavehvash, Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    In this paper, we divide the imaging geometry of a photoacoustic computed tomography (PACT) structure that have a circular geometry and have focused transducers of positive or negative focus, into different zones of varying resolution. With using the presented analysis, it is possible to find the maximum range in which the system resolution is at its best value, according to the device specifications. The following equations are used to find the blind spot angles of the system for each source point inside the chamber. These are important for two reasons: the first is that the user can calculate the range in which the imaging system has the best quality by entering the specifications of his... 

    Computer Simulation of Ultrasonic Waves in Cybernetic Glasses in Order to Increasing Spatial Resolution of Blinds

    , M.Sc. Thesis Sharif University of Technology Monajatipour, Fahimeh (Author) ; Amjadi, Ahmad (Supervisor)
    Eyesight is one of the most important tools for humans to communicate with environment and consequently, blindness or poor eyesight results in unsatisfactory effect on life quality. Owing to the importance of the sense and to assist to the patients, this thesis aims to design and assemble cybernetic glasses using ultrasound waves. To this end, firstly, the notion of waves focusing on ultrasound waves is described and reactions of human hearing system to the waves are studied. Then, the transducers as a key device are introduced. Afterward, bat sense system to communicate with environment which is based ultrasound waves is described. Next, attenuation effects on ultrasound wave pressures are... 

    Study of the behavior of ultrasonic piezo-ceramic actuators by simulations

    , Article Electronic Materials Letters ; Vol. 10, Issue. 1 , 2014 , pp. 37-42 ; ISSN: 17388090 Abdullah, A ; Pak, A ; Abdullah, M. M ; Shahidi, A ; Malaki, M ; Sharif University of Technology
    In recent years, there has been a growing interest in the simulation and analysis of piezoelectric transducers with the he help of equivalent electrical circuit simulations (EECS). This paper has been devoted to study of such approach for two designed and fabricated ultrasonic sandwich transducers. By using analytical analysis, the dimensions of components of the two piezoelectric transducers were determined for the assumed resonance frequencies of 30 kHz and 40 kHz. Then, by using a two dimensional finite element model, and regarding two different modeling techniques for the transducers and by application of a current source which was connected directly to the piezoelectric pieces of the... 

    Design of a broadband high frequency ultrasound transducer for skin imaging

    , Article 6th RSI International Conference on Robotics and Mechatronics, IcRoM 2018, 23 October 2018 through 25 October 2018 ; 2019 , Pages 261-265 ; 9781728101279 (ISBN) Babazadeh Khameneh, A ; Chabok, H. R ; Nejat, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    This paper discusses the design of a high frequency wide bandwidth ultrasound transducer with the center frequency of 50 MHz and an aperture diameter of 3 mm for medical ultrasonic imaging. The piezoelectric material used in this design is Lithium Niobate. The design is verified by both KLM equivalent circuit and spatial impulse response method as used in FIELD II software and the theoretical imaging resolution has been calculated as 50 um axially and 80 um laterally. The possible applications of this probe are skin layer imaging, tumor detection and superficial blood flow measurement  

    Elemental field distributions in corrugated structures with large-amplitude gratings

    , Article Electronics Letters ; Volume 39, Issue 23 , 2003 , Pages 1690-1691 ; 00135194 (ISSN) Manzuri Shalmani, M. T ; Baghai Wadji, A. R ; Sharif University of Technology
    A unified and robust method has been introduced to compute magnetostatic and electrostatic fields for nonperiodic excitations in periodically corrugated anisotropic structures. The method extends a previously published concept of modified phased-periodic Green's functions for solving flat-surface problems. Convergent results have been obtained for corrugations with aspect ratios exceeding 15. Novel elemental field distributions are presented as examples  

    Ultrasound dosimetery using microbubbles

    , Article IFMBE Proceedings, 20 June 2011 through 23 June 2011 ; Volume 35 IFMBE , June , 2011 , Pages 359-362 ; 16800737 (ISSN) ; 9783642217289 (ISBN) Rezayat, E ; Zahedi, E ; Tavakkoli, J ; Sharif University of Technology
    In this paper, a new technique based on nonlinear resonance of microbubbles is investigated in order to estimate the amplitude of an ultrasound wave pressure field. First, the existing theoretical model is reviewed. Then, an experimental setup consisting of a bubble generator and transmitting/receiving ultrasound transducers operating in the 1 MHz frequency range is described. The effect of background noise is also taken into account. Results show that the second harmonic oscillations are detectable, paving the way to develop a quantitative method for in vivo calibration of ultrasound waves  

    Optimized integrated design of a high-frequency medical ultrasound transducer with genetic algorithm

    , Article SN Applied Sciences ; Volume 3, Issue 6 , 2021 ; 25233971 (ISSN) Babazadeh Khameneh, A ; Chabok, H. R ; Nejat Pishkenari, H ; Sharif University of Technology
    Springer Nature  2021
    Designing efficient acoustic stack and elements for high-frequency (HF) medical ultrasound (US) transducers involves various interrelated parameters. So far, optimizing spatial resolution and acoustic field intensity simultaneously has been a daunting task in the area of HF medical US imaging. Here, we introduce optimized design for a 50-MHz US probe for skin tissue imaging. We have developed an efficient design and simulation approach using Krimholtz, Leedom and Matthaei (KLM) equivalent circuit model and spatial impulse response method by means of Field II software. These KLM model and Field II software are integrated, and a GA algorithm is used to optimize the design of the US transducer... 

    A novel sensitive aptamer-based nanosensor using rGQDs and MWCNTs for rapid detection of diazinon pesticide

    , Article Journal of Environmental Chemical Engineering ; Volume 9, Issue 1 , 2021 ; 22133437 (ISSN) Fooladi Talari, F ; Bozorg, A ; Faridbod, F ; Vossoughi, M ; Sharif University of Technology
    Elsevier Ltd  2021
    An optical apta-nanosensor was designed and developed based on reduced graphene quantum dots (rGQDs) and multi-walled carbon nanotubes (MWCNTs) and applied for the selective detection of diazinon as one of the most widely used organophosphorus pesticides. Considering the GQDs and rGQDs high fluorescence emission and optical stability, efficient optical transducers could be designed and precise detection methods could be developed based on such transducers. Herein, by using rGQDs, diazinon specific aptamer, and MWCNTs, a simple economical fluorescence method has been introduced to detect and measure diazinon with the detection limit of 0.4 nM (0.1 μg/L) in the range of 4-31 nM, meeting the... 

    Blind angle and angular range detection in planar and limited-view geometries for photoacoustic tomography

    , Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 922-926 ; 9781665433655 (ISBN) Hakakzadeh, S ; Kavehvash, Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    In this paper, the relationship between the position of ultrasound transducers from the photoacoustic source and the reconstructed image is investigated. Our studies have shown that the distance of the transducer and its location from the photoacoustic source specifically affects and is closely related to the quality of the reconstructed image of the source. Also, we introduce a concept called blind angle for photoacoustic computed tomography (PACT) that have planar or circular limited-view geometry. Complete and accurate equations of this relationship are presented in this paper for all different 2D photoacoustic geometries. The main source of these equations is the spherically of the... 

    Design and simulation of a microfluidic device for acoustic cell separation

    , Article Ultrasonics ; Volume 84 , March , 2018 , Pages 234-243 ; 0041624X (ISSN) Shamloo, A ; Boodaghi, M ; Sharif University of Technology
    Elsevier B.V  2018
    Experimental acoustic cell separation methods have been widely used to perform separation for different types of blood cells. However, numerical simulation of acoustic cell separation has not gained enough attention and needs further investigation since by using numerical methods, it is possible to optimize different parameters involved in the design of an acoustic device and calculate particle trajectories in a simple and low cost manner before spending time and effort for fabricating these devices. In this study, we present a comprehensive finite element-based simulation of acoustic separation of platelets, red blood cells and white blood cells, using standing surface acoustic waves... 

    Inastantaneous baseline multiple damage detection and localization in an aluminum plate using Lamb waves

    , Article 30th Congress of the International Council of the Aeronautical Sciences, 25 September 2016 through 30 September 2016 ; 2016 ; 9783932182853 (ISBN) Alem, B ; Abedian, A ; Nasiri, M ; Sharif University of Technology
    International Council of the Aeronautical Sciences 
    In recent years, new Structural Health Monitoring (SHM) methodologies with a concept of "instantaneous baseline damage detection" are being developed by many researchers. In this context, this paper uses a new method to identify multiple damage in the aluminum plate. For this goal use from spars PZWS sensor network to generate and received guided waves. Ultrasonic waves are generated and measured from all possible different pairs of excitation and sensing transducers. For feature extraction of received signals used from continues wavelet transform. A probabilistic damage diagnostic algorithm based on correlation analysis was investigated to locate single or multiple damages. In this study,... 

    Simulation of blood particle separation in a trapezoidal microfluidic device by acoustic force

    , Article IEEE Transactions on Electron Devices ; Volume 66, Issue 3 , 2019 , Pages 1495-1503 ; 00189383 (ISSN) Shamloo, A ; Yazdan Parast, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Nowadays, the importance of the blood particles separation is undeniable in medical fields and there are different sorts of separation methods accordingly. Acoustic cell separation is chosen in this paper. Also, numerical methods have been used to study the effect of geometrical factors on the separation of the particles before spending time and expenses in a trial and error manner experimentally. We have implemented a plenary finite-element-based simulation of separatingblood particles such as white blood cells and platelets in an acoustic field using standing surface acoustic waves. In this paper, unlike previous works in which the channel is rectangular; the channel is trapezoidal in... 

    Altered expression of STAT genes in periodontitis

    , Article Human Antibodies ; Volume 29, Issue 3 , 2021 , Pages 209-216 ; 10932607 (ISSN) Gholami, L ; Movafagh, A ; Badrlou, E ; Nazer, N ; Yari, M ; Sadeghi, G ; Mirzajani, S ; Shadnoush, M ; Sayad, A ; Ghafouri Fard, S ; Sharif University of Technology
    IOS Press BV  2021
    Signal Transducer and Activator of Transcription (STAT) pathway is functionally located downstream of Janus kinases proteins and can integrate signals from diverse pathways, thus regulating several aspects of immune responses. Although contribution of STAT proteins in the pathogenesis of several inflammatory conditions has been confirmed, their role in the development of periodontitis has been less appraised. Thus, we assessed levels of STAT transcripts in the periodontal tissues and circulation of affected individuals compared with the corresponding controls. Expression of STAT1 was remarkably lower in tissues samples of patients compared with control tissues (Ratio of mean expression (RME)... 

    A Brief Investigation on the Effects of Metallic and Composite Patches on the Behavior of Aged Parts Using Numerical Methods (FEM) and Lamb Waves Propagation

    , M.Sc. Thesis Sharif University of Technology Mollaei, Fouad (Author) ; Abedian, Ali (Supervisor)
    The main purpose of this text is to develop a method for health monitoring of patch-repaired structures. The method consists of usage of piezoelectric wafer active sensors (PWAS) in the mean of stress waves in plate-like structures and processing the obtained results gathered from these sensors using finite element method. During this analysis, effect of different parameters has been investigated by sensitivity analysis methods. The main kind of stress waves that used are lamb wave of different kind. The behavior of main structure due to propagation of symmetric and anti-symmetric modes of lamb wave was investigated. Beginning with finding the results of un-damaged and un-repaired... 

    Monitoring pipeline vibration due to cavitation through an orifice by piezoelectric sensor

    , Article Advanced Materials Research ; Volume 403-408 , 2012 , Pages 3418-3423 ; 10226680 (ISSN) ; 9783037853122 (ISBN) Rad, F. P ; Zabihollah, A ; Sharif University of Technology
    Pipelines are one of the most important and efficient ways for transporting energy like water, gas, oil and etc. between different places all across the world. As these pipelines are located in different conditions and situations, they are all sensitive to a wide variety of damages like vibration, so monitoring their structural behavior is an essential task. Monitoring pipeline vibration caused by cavitation through an orifice by a piezoelectric sensor is presented in this paper  

    Modeling and simulation of graspers force in minimally invasive surgery

    , Article 2009 International Association of Computer Science and Information Technology - Spring Conference, IACSIT-SC 2009, Singapore, 17 April 2009 through 20 April 2009 ; 2009 , Pages 475-479 ; 9780769536538 (ISBN) Hortamani, R ; Zabihollah, A ; Sharif University of Technology
    In Minimally Invasive Surgery (MIS) the operation is performed through introducing surgery instruments, graspers, scissor into the body. In the present work, a novel smart grasper is presented in which the surgeon can virtually acquire a feeling of force/momentum experienced by the organ/tissue. The smart grasper uses piezoelectric sensors bonded at desired locations to detect the applied force/momentum by surgeon and to measure the transmitted response to the tissue/organ. © 2009 IEEE  

    Pressure loss in a horizontal two-phase slug flow

    , Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 132, Issue 7 , 2010 , Pages 0713041-0713048 ; 00982202 (ISSN) Kabiri Samani, A. R ; Borghei, S. M ; Sharif University of Technology
    The study of air-water, two-phase flows in hydraulic structures such as pressurized flow tunnels, culverts, sewer pipes, junctions, and similar conduits is of great importance for design purposes. Air can be provided by vortices at water intakes, pumping stations, aerators, steep channels, etc. Under certain conditions, air may also be introduced into pressurized intake systems, which may form large bubbles in portions of the pipe. The bubbles may, in turn, cause an unstable slug flow, or other flow patterns, that leads to sever periodic transient pressure. In this paper, an experimental model (a circular and transparent pipeline, 90 mm in ID and 10 m in length) is used to predict pressure...