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    Dynamic signal quality index for electrocardiograms

    , Article Physiological Measurement ; Volume 39, Issue 10 , 2018 ; 09673334 (ISSN) Yaghmaie, N ; Maddah Ali, M. A ; Jelinek, H. F ; Mazrbanrad, F ; Sharif University of Technology
    Institute of Physics Publishing  2018
    Objective: The advent of telehealth applications and remote patient monitoring has led to an increasing need for continuous signal quality monitoring to ensure high diagnostic accuracy of the recordings. Cardiovascular diseases often manifest electrophysiological anomalies, therefore the electrocardiogram (ECG) is one of the most used signals for diagnostic applications. Various types of noise and artifacts are not uncommon in ECG recordings and assessing the quality of the signal is essential prior to any clinical interpretation. In this study, a dynamic signal quality index (dSQI) is introduced using a new time-frequency template-based approach. Approach: A smoothed pseudo Wigner-Ville... 

    On time-constant robust tuning of fractional order U+005B proportional derivative U+005D controllers

    , Article IEEE/CAA Journal of Automatica Sinica ; 2017 ; 23299266 (ISSN) Badri, V ; Tavazoei, M. S ; Sharif University of Technology
    This paper deals with analyzing a newly introduced method for tuning of fractional order U+005B proportional derivative U+005D U+0028 FO U+005B PD U+005D U+0029 controllers to be used in motion control. By using this tuning method, not only the phase margin and gain crossover frequency are adjustable, but also robustness to variations in the plant time-constant is guaranteed. Conditions on the values of control specifications U+0028 desired phase margin and gain crossover frequency U+0029 for solution existence in this tuning method are found. Also, the number of solutions is analytically determined in this study. Moreover, experimental verifications are presented to indicate the... 

    Power and frequency analysis for data and control independence in embedded processors

    , Article 2011 International Green Computing Conference and Workshops, IGCC 2011, 25 July 2011 through 28 July 2011 ; July , 2011 , Page(s): 1 - 6 ; 9781457712203 (ISBN) Samie, F ; Baniasadi, A ; Sharif University of Technology
    In this work we study control independence in embedded processors. We classify control independent instructions to data dependent and data independent and measure each group's frequency and behavior. Moreover, we study how control independent instructions impact power dissipation and resource utilization. We also investigate control independent instructions' behavior for different processors and branch predictors. Our study shows that data independent instructions account for 34% of the control independent instructions in the applications studied here. We also show that control independent instructions account for upto 12% of the processor energy and 15.6%, 11.2% and 8.6% of the instructions... 

    Feature extraction from optimal time-frequency and time-scale transforms for the classification of the knee joint vibroarthrographic signals

    , Article 3rd IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2003, 14 December 2003 through 17 December 2003 ; 2003 , Pages 709-712 ; 0780382927 (ISBN); 9780780382923 (ISBN) Eskandari, H ; Shamsollahi, M. B ; Rahimi, A ; Behzad, M ; Afkari, P ; Zamani, E. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    In this study knee joint vibroarthrographic (VAG) signals are recorded during active knee movements, which are essentially non-stationary. Because of this nature, common frequency methods are unable to represent the signals, accurately. Both time-frequency and time-scale transforms are used in this research which are good tools for studying non-stationary signals. By optimizing the utilized transforms, it was concluded that the wavelet packet, having the ability of multiresolutional analysis, is a more promising method to extract features from the VAG signals. The performance of different feature extraction techniques were compared by using three new recorded and extensive databases,... 

    Generalizability of trunk muscle EMG and spinal forces

    , Article IEEE Engineering in Medicine and Biology Magazine ; Volume 20, Issue 6 , 2001 , Pages 72-81 ; 07395175 (ISSN) Sparto, P. J ; Parnianpour, M ; Sharif University of Technology
    The generalizability of trunk muscle EMG and spinal loading estimates obtained from an EMG-assisted biomechanical model was assessed over three occasions and three repetitions. The greatest sources of variability consisted of the intersubject differences and the interaction between subject and occasion. The ID (reliability coefficient) was less for trunk muscle activity compared with estimates of anteroposterior shear force, compression force, and gain computed from the biomechanical model. In order to obtain an ID of 0.8, we recommend five testing occasions for submaximal EMG measurements and three testing occasions for biomechanical estimates. Reproducible estimates of maximal trunk... 

    A two dimensional wavelet packet approach for ECG compression

    , Article 6th International Symposium on Signal Processing and Its Applications, ISSPA 2001, Kuala Lumpur, 13 August 2001 through 16 August 2001 ; Volume 1 , 2001 , Pages 226-229 ; 0780367030 (ISBN); 9780780367036 (ISBN) Moghaddam, A. R. A ; Nayebi, K ; Sharif University of Technology
    IEEE Computer Society  2001
    An improved compression algorithm for ECG signals is presented using temporal alignment of beats and 2-D wavelet packet transform (WPT). This 2-D transform based approach utilizes the fact that the electrocardiogram (ECG) signals generally show two types of correlation, namely correlation between subsequent samples within each ECG cycle (intrabeat) and correlation between subsequent cycles (interbeat). One simple compression algorithm in the 2-D WPT domain, which is applied to some records in the MIT-BIH arrhythmia database shows lower percent root mean square difference (PRD) than 1-D wavelet based compression methods for the same compression ratio (CR). © 2001 IEEE  

    Experimental Study of Boundary Layer Transition on a Swept Wing

    , Ph.D. Dissertation Sharif University of Technology Masdari, Mehran (Author) ; Soltani, Mohammad Reza (Supervisor) ; Ghorbanian, Kaveh (Supervisor)
    Swept wings are of great interest for achieving high speed as well as increasing the critical Mach number in aircrafts and unmanned flying vehicles. The governing fluid mechanical phenomenon on swept wings is strongly influenced by the chordwise and spanwise components of the cross-flow. Laminar airfoils are employed for drag reduction and postponing the boundary layer transition from laminar to turbulence. Hence, the knowledge about the boundary layer structure and instability modes is of great significance. A series of wind tunnel tests are performed to examine the flow field over a swept wing at various conditions. The wing has a laminar flow airfoil section similar to NACA 6-series ones.... 

    Effect of Delta Wing Leading Edge Vortex on Pressure Distribution of Fuselagein in Subsonic Regime

    , M.Sc. Thesis Sharif University of Technology Sadri, Vahid (Author) ; Soltani, Mohammad Reza (Supervisor) ; Ghorbanian, Kaveh (Supervisor)
    The delta wing has proven to be very useful for the study and understanding of the basic features of separation-induced vortex flows since many aspects of these vortex flows can be generated with this simple shape. A phenomenon of special importance to vortical flows is vortex breakdown. Vortex breakdown remains an important and complicated phenomenon that can have negative or positive effects. The delta wing leading edge vortex is emphases in many experiments. Most of these experiments are focused on the delta wing only.In this research, emphasis is on vortex interaction of delta wing-canard-fuselage configuration. A series of low speed wind tunnel tests were carried out to investigate... 

    Effects of Reduced Frequency and Mean Angle of Attack on Pressure Distribution of a Supercritical Airfoil under Plunging Motion in Low-Subsonic Flow

    , M.Sc. Thesis Sharif University of Technology Zaynalzadeh, Aghil (Author) ; Soltani, Mohammad Reza (Supervisor)
    A ten percent thick supercritical airfoil, having special previllage rather than conventional airfoils tested in a low speed wind tunnel to measure pressure distribution over the airfoil in steady and unsteady flow. Present thesis is set out to discuss effects of reduced frequency and mean angle of attack on pressure distribution during plunging motion in low-subsonic flow. Investigation of experimental data from frequency domain aspect is very challenging area in experimental aerodynamics. Therefore, the concepts of frequency domain analysis is pointed out. The analysis of experiment data is devidind in two different part, that is, steady and unsteady flow. Flow separation over the airfoil... 

    Experimental Investigation of the Roughness Effects on the Pressure Distribution and Stationary Crossflow Instability over a Swept wing

    , M.Sc. Thesis Sharif University of Technology Damghani, Hamid (Author) ; Soltani, Mohammad Reza (Supervisor)

    Wind tunnel experiments are conducted to evaluate surface pressure distribution over a semi span swept wing with sweep angle of 33 degrees. The wing section has a laminar flow airfoil similar to that of NACA 6-series airfoils. The tests were conducted at speeds ranging from 50 to 70m/s with and without surface roughness. Surface static pressure was measured on the wing upper surface at three different chordwise rows located at the inboard station, (section 1, 2y/b=0.2), middle station, (section 2, 2y/b=0.43), and outboard station, (section 3, 2y/b=0.78). The differences between pressure distributions on the three sections of the wing were studied and the experimental results showed that... 

    The effect of fractional order on oscillatory behavior of scalar fractional delay systems of neutral type

    , Article IFAC Proceedings Volumes (IFAC-PapersOnline) ; February , 2013 , Pages 480-485 ; 14746670 (ISSN); 9783902823274 (ISBN) Mesbahi, A ; Haeri, M ; Sharif University of Technology
    The undamped oscillations of a scalar fractional neutral system are studied in this paper. For this purpose, it is proved that this kind of systems can have the oscillatory behavior. The necessary and sufficient condition is proposed to determine that there exists a delay value for which the system oscillates. The frequency, amplitude and required delay for the undamped oscillations depend on the fractional order. However, the behavior of dependencies is not specified. Indeed, when the system has oscillatory behavior, it is bounded-input bounded-output stable for delay less than the required delay. Moreover, when the order is approaching to an integer value, the necessary and sufficient... 

    Analytical mode distributions and resonant frequencies in ladder networks used in power combining oscillator arrays

    , Article Scientia Iranica ; Volume 15, Issue 2 , 2008 , Pages 175-181 ; 10263098 (ISSN) Akbarpour, M. H ; Banai, A ; Farzaneh, F ; Sharif University of Technology
    Sharif University of Technology  2008
    An analysis of resonant modes in ladder networks is performed using difference equations. Linear and loop configurations are studied and analytical relations are derived for the mode distributions and resonant frequencies of these networks, having arbitrary elements. Furthermore, it is shown that a) Modes with an exponential distribution along network nodes may exist in some cases and b) The mode distributions in loop networks are independent of network elements. Finally, a simple criterion is obtained for a loop structure to control the spacing between resonant frequencies. © Sharif University of Technology, April 2008  

    Modal parameters identification using bilinear joint time-frequency analysis

    , Article International Conference on Noise and Vibration Engineering 2006, ISMA 2006, Heverlee, 18 September 2006 through 20 September 2006 ; Volume 5 , 2006 , Pages 2907-2919 Roshan Ghias, A ; Mobed, M ; Shamsollahi, M. B ; Behzad, M ; Sharif University of Technology
    Katholieke Universiteit Leuven  2006
    In this paper, a new method for modal parameter estimation using time-frequency representations is presented. Smoothed Pseudo Wigner-Ville representation which is a member of the Cohen's class distributions is used that reduces cross-terms in time-frequency plane dramatically and holds resolution as well. The method was applied to systems with high damping, and the results were superior to other conventional methods. © (2006) by the Katholieke Universiteit Leuven Department of Mechanical Engineering All rights reserved  

    Application of exact continuum size-dependent theory for stability and frequency analysis of a curved cantilevered microtubule by considering viscoelastic properties

    , Article Engineering with Computers ; Volume 37, Issue 4 , 2021 , Pages 3629-3648 ; 01770667 (ISSN) Shariati, A ; Habibi, M ; Tounsi, A ; Safarpour, H ; Safa, M ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    The stability analysis of cantilevered curved microtubules in axons regarding various size elements and using the generalized differential quadrature method for solving equations is reported. The impacts of covering MAP Tau proteins along with cytoplasm are taken into account as the elastic medium. Curved cylindrical nanoshell considering thick wall is used to model the microtubules. The factor of length scale (l/R = 0.2) used in modified couple stress theory would result in more accuracy when it comes to comparison with experiments, while alternative theories presented in this paper provide less precise outcomes. Due to the reported precise results, at the lower value of the time-dependent... 

    Detection of sudden structural damage using blind source separation and time-frequency approaches

    , Article Smart Materials and Structures ; Volume 25, Issue 5 , 2016 ; 09641726 (ISSN) Morovati, V ; Kazemi, M. T ; Sharif University of Technology
    Institute of Physics Publishing  2016
    Seismic signal processing is one of the most reliable methods of detecting the structural damage during earthquakes. In this paper, the use of the hybrid method of blind source separation (BSS) and time-frequency analysis (TFA) is explored to detect the changes in the structural response data. The combination of the BSS and TFA is applied to the seismic signals due to the non-stationary nature of them. Firstly, the second-order blind identification technique is used to decompose the response signal of structural vibration into modal coordinate signals which will be mono-components for TFA. Then each mono-component signal is analyzed to extract instantaneous frequency of structure. Numerical... 

    An Exp. Study of the Effect of Sweep on the Wake of a 2-D Wing

    , M.Sc. Thesis Sharif University of Technology Yousefi, Ramin (Author) ; Soltani, Mohammad Reza (Supervisor)
    In this experimental study, a series of wind tunnel tests were performed to examine the wake flow profile over three swept wings with sweep angles of 23, 33 and 40 degrees with similar aspect ratio at various conditions. The airfoil of wing was a NACA 6-series airfoil designed to provide a laminar flow on the front half of the airfoil. The tests, made at a mid aerodynamic chord Reynolds number of 8×〖10〗^5, covered an angle of attack range of -2 to 10 degree. The wing tip vortex effects are eliminated by placing an End-plate on the wing tip.The tests were carried out at two main section of wing and two various position from behind of wing. A total pressure rake and transducers was used to... 

    Torsional Vibration Modeling and Measurement in Single Rotor Machinery for Fault Diagnosis

    , M.Sc. Thesis Sharif University of Technology Hosseini, Alireza (Author) ; Behzad, Mahdi (Supervisor) ; Mahdigholi, Hamid (Supervisor)
    Experimental investigation of drillstring dynamics is essential to complete the theoretical studies and to alleviate complexity of such dynamic models. Vibration is one of the most effective parameter affecting drilling operation. Most of the experimental setups are looking for drilling mud tests, operational characteristics of bit under several bad condition and bit mud stone interaction in drilling operation and there are few setups to study vibration of the drilling setups. In this project a test rig has been introduce which is a scale of a real industrial drilling rig by the factor of 10300. Then based on the field studies of drilling failures in Iranian oil drilling rig , a crack has... 

    Nonlinear Dynamic Analysis of PDMS Micro Sensors based on Strain Gradient Theory

    , Ph.D. Dissertation Sharif University of Technology Taheran, Farshad (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Firoozbakhsh, Keikhosrow (Supervisor)
    In this research, a viscoelastic microcantilever beam is analytically analyzed based on the modified strain gradient theory and the results are used in order to study micro pillar shear stress sensors. The abstract of this research can be divided to three sections:In the first section, applying Euler-Bernoulli inextensibility of the centerline condition via Hamilton’s principle, the nonlinear equation of motion and related boundary conditions are derived based on shortening effect theory and discretized by Galerkin method. Inner damping, nonlinear curvature effect, and nonlinear inertia terms are applied. First mode nonlinear frequency and time response of the viscoelastic microcantilever... 

    Frequency Analysis of the Wake of an Oscillating Airfoil

    , M.Sc. Thesis Sharif University of Technology Shariloo, Koosha (Author) ; Ebrahimi, Abbas (Supervisor)
    Understanding the physics of unsteady flow is very important due to various applications. Axial compressors, turbines, helicopter blades, and energy harvesters are the essential applications of this problem. An airfoil under pitching oscillation is one of the common cases in unsteady aerodynamics, and several characteristics of the flow around it have been investigated up to now. The frequency analysis of the wake flow for pitching airfoils has received less attention. In this research, experimental tests have been carried out for symmetric airfoil NACA 0012 under pitching oscillation in low Reynolds flow (6×104) and before the airfoil stall condition. The experiments were carried out in the... 

    Evaluation of flapping wing propulsion based on a new experimentally validated aeroelastic model

    , Article Scientia Iranica ; Volume 19, Issue 3 , 2012 , Pages 472-482 ; 10263098 (ISSN) Pourtakdoust, S. H ; Aliabadi, S. K ; Sharif University of Technology
    To evaluate the propulsion system capabilities of a Flapping Micro Air Vehicle (FMAV), a new aeroelastic model of a typical flexible FMAV is developed, utilizing the Euler-Bernoulli torsion beam and quasi steady aerodynamic model. The new model accounts for all existing complex interactions between the mass, inertia, elastic properties, aerodynamic loading, flapping amplitude and frequency of the FMAV, as well as the effects of several geometric and design parameters. To validate the proposed theoretical model, a typical FMAV, as well as an instrumented test stand for the online measurement of forces, flapping angle and power consumption, has been constructed. The experimental results are...