Search for: noise-reductions
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    An adaptive filter for noise cancelling in mammography images based on Cellular Automata

    , Article International Review on Modelling and Simulations ; Volume 5, Issue 3 , June , 2012 , Pages 1322-1326 ; 19749821 (ISSN) Farrokhbakht, H ; Masoumzadeh Tork, A ; Yazdan Talab, E ; Ramezanpour, H ; Darmani, G ; Sharif University of Technology
    In recent years, several techniques based on repetition of the image are used to remove noise. In this paper a new method based on Cellular Automata for image noise removal in mammography images is recommended. We present a new formulation that makes improvements. The formulation uses a neighborhood with sizes and format adapted to the features of the image on reconstruction. We demonstrated through experiments and comparison with other common used techniques that this procedure produces excellent results for the problem of restoring true color images  

    A method for noise reduction in active-rc circuits

    , Article IEEE Transactions on Circuits and Systems II: Express Briefs ; Volume 58, Issue 12 , 2011 , Pages 906-910 ; 15497747 (ISSN) Gharibdoust, K ; Bakhtiar, M. S ; Sharif University of Technology
    A method for noise reduction in active-$RC$ circuits is introduced. It is shown that the output noise in an active-$RC$ circuit can be considerably reduced, without disturbing the circuit transfer function by inserting appropriate passive or active components in the circuit. The inserted components introduce new signal paths in the circuit for noise reduction while the original circuit transfer function is kept unchanged. The procedure to define the proper paths in the circuit and their transfer functions is given. The effectiveness of the presented method is demonstrated using a second-order active-RC filter fabricated in a 0.18-$ {m}$ CMOS technology  

    A comprehensive study on noise reduction methods of marine propellers and design procedures

    , Article Applied Acoustics ; Volume 150 , 2019 , Pages 55-69 ; 0003682X (ISSN) Ebrahimi, A ; Razaghian, A. H ; Seif, M. S ; Zahedi, F ; Nouri Borujerdi, A ; Sharif University of Technology
    Elsevier Ltd  2019
    The noise generated by the propeller is one of the most important components of the vessels noise. Therefore, reducing this noise will significantly decrease the total noise of the vessel. Underwater noise of vessels has destructive effects on marine life. In addition, this noise affects the health and comfort of the crew and passengers of the ship. Moreover, high noise may cause warships to be detected easily. In this paper, first, common methods of noise reduction, including blade coating, modern propellers, propeller hub modification and ducted propellers are investigated. Then, relevant optimization methods are presented. Next, the effects of the geometric parameters like number of... 

    Sparse Decomposition of two Dimensional Signals and Its Application to Image Enhancement

    , M.Sc. Thesis Sharif University of Technology Ghaffari, Aboozar (Author) ; Babaie Zadeh, Massoud (Supervisor)

    A novel algorithm for impulse noise classification in digital images

    , Article International Review on Computers and Software ; Volume 4, Issue 6 , 2009 , Pages 627-632 ; 18286003 (ISSN) Vahdat Nejad, H ; Tork Ladani, B ; Zamanifar, K ; Nematbakhsh, N ; Sharif University of Technology
    Noise reduction is a major concern in digital image processing systems, which have been investigated by several techniques. One kind of important noises in images is known as Salt & Pepper, which may have different causes. In this paper a new approach for eliminating this type of noise is presented. The approach is different from all previous works in this field, and is based on classification. More precisely, it tries to classify pixels of an image to one of two categories: noisy or not noisy. Afterward, it employs a median filter for pixels which have been classified as noisy, and remains others unchanged; hence, edges and other fine details are kept. Experimental results show this... 

    An Investigation of Signal Processing Techniques for Monitoring of the Heart Abnormalities

    , M.Sc. Thesis Sharif University of Technology Ghotbi Ravandi, Amir (Author) ; Ghorshi, Alireza (Supervisor)
    In this thesis we have investigated and improved the signal processing techniques which are used for monitoring the heart abnormalities in terms of ECG (ElectroCardioGram) signals in order to detect heart attacks before they occur. De-noising ECG signals are one of the most important research topics in computer and electrical engineering fields. There are many different algorithms for de-noising signals in various domains. It usually is needed to propose a suitable algorithm for each specific system. In some cases instead of developing a new algorithm, we could modify the available ones for de-noising in our system. ECG signals are output from an electrocardiograph which measures electrical... 

    Gearbox Vibrations Analysis for Noise Reduction through Computer Aided Engineering

    , M.Sc. Thesis Sharif University of Technology Ramezani Farani, Ali (Author) ; Saadatfoumani, Mahmoud (Supervisor)
    Millions of people are exposed to vehicle noise at their work or residence environment daily and as a result their physical and mental healths get in danger. Subsequently the vehicle noise and vibration become an important factor in vehicle quality. Gearbox is a main element in vehicle powertrain and also an important source of noise and vibration. So inspection of vibration and noise in Gearbox and attempting to reduce it will help to reduce vehicle noise and vibration. This project is based on a deal between sharif university of technology and industry in which the target was to make improvement in every source of noise and vibration in a specific vehicle. The aim of this project is to... 

    A new pipeline implementation of an adaptive IIR filter for noise reduction application

    , Article IEEE International Symposium on Communications and Information Technologies: Smart Info-Media Systems, ISCIT 2004, Sapporo, 26 October 2004 through 29 October 2004 ; Volume 1 , 2004 , Pages 577-581 ; 0780385934 (ISBN) Golmohammadi, A ; Manzuri, M. T ; Ayat, S ; Sharif University of Technology
    the parallel form in adaptive HR filtering is an efficient realization that provides robust stability monitoring with less complexity than that of the direct form. This paper presents an implementation of two line parallel structure employing a real orthogonal transform and real coefficients second-order section as sub filters on FPGA. Architecture that is implemented is in pipeline fashion and it is independent from its building blocks and they may have its own implementation or in other system numbering. In the last section, we compared throughput of our architecture with a Ti DSP (TMS320C3x/4x), the results show that this architecture works better than the DSP  

    A 1.8-V high-speed 13-bit pipelined analog to digital converter for digital IF applications

    , Article Proceedings of the 2003 IEEE International Symposium on Circuits and Systems, Bangkok, 25 May 2003 through 28 May 2003 ; Volume 1 , 2003 , Pages I885-I888 ; 02714310 (ISSN) Aslanzadeh, H. A ; Mehrmanesh, S ; Vahidfar, M. B ; Atarodi, M ; Sharif University of Technology
    A 1.8-v 13-bit 25MS/S pipelined analog-to-digital (A/D) converter was designed and simulated using 0.18um CMOS technology. The proposed new high speed low power class AB opamp makes it possible to achieve requirements of 13-bit resolution and settling in 12ns within 0.01% accuracy. An optimum architecture for noise and power consideration is also selected to reduce power. Total Power dissipation is about 82 mw from a single 1.8 v supply, where INL and DNL are 0.7 LSB and 0.6 LSB respectively. SNDR of 75.5 dB is achieved  

    A new low-power sigma-delta modulator with the reduced number of op-amps for speech band applications

    , Article Proceedings of the 2003 IEEE International Symposium on Circuits and Systems, Bangkok, 25 May 2003 through 28 May 2003 ; Volume 1 , 2003 , Pages I1033-I1036 ; 02714310 (ISSN) Safarian, A. Q ; Sahandi, F ; Mojtaba Atarodi, S ; Sharif University of Technology
    An area and power-efficient second order sigma-delta modulator is presented. At system level, we propose a new single-loop single-stage modulator that uses only one class-AB op-amp to realize a second order noise shaping for speech band applications. The modulator shows 86 dB DR in 4 kHz speech bandwidth. It consumes 125 μw from a 2.5 V supply  

    Comparison of noise reduction techniques in RF SQUID magnetic detection systems

    , Article Proceedings - 2010 18th Iranian Conference on Electrical Engineering, ICEE 2010, 11 May 2010 through 13 May 2010 ; 2010 , Pages 446-449 ; 9781424467600 (ISBN) Sadeghi Jahed, N. M ; Sarreshtedari, F ; Forooghi, F ; Fardmanesh, M ; Schubert, J ; Banzet, M ; Sharif University of Technology
    The noise level of the magnetometer and gradiometer RF SQUIDs were investigated using different shielding methods. The used methods include different active and passive shielding, such as Helmholtz configurations, locally compensation coils, superconducting bulks and μ-metal shields. For the passive shielding approach, using FEM simulation we have investigated the shielding effectiveness of superconducting bulks versus the use of μ-metal shielding. The superconducting shield is a YBCO circular bulk, which was made using melt-texture method and located in a distance in front of the SQUID. In this work the results of these shielding methods are presented and compared, while their effectiveness... 

    A new lattic LP-based post filter for adaptive noise cancellers in mobile and vehicular applications

    , Article Proceedings of the 8th IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2008, 16 December 2008 through 19 December 2008, Sarajevo ; 2008 , Pages 407-412 ; 9781424435555 (ISBN) Khorram, S ; Sameti, H ; Veisi, H ; Abutalebi, H. R ; Sharif University of Technology
    Adaptive Noise Cancellation (ANC) is a well-known technique for background noise reduction in automobile and vehicular environments. The noise fields in automobile and other vehicle interior obey the diffuse noise field model closely. On the other hand, the ANC does not provide sufficient noise reduction in the diffuse noise fields. In this paper, a new multistage post-filter is designed for ANC as a solution to diffuse noise conditions. The designed post-filter is a single channel Linear Prediction (LP) based speech enhancement system. The LP is performed by an adaptive lattice filter and attempts to extract speech components by using intermediate ANC signals. The post-filter has no... 

    Design and Fabrication of Nanovolt Ag/AgCl Bio-potential Sensor

    , M.Sc. Thesis Sharif University of Technology Rostami, Behnoush (Author) ; Fardmanesh, Mehdi (Supervisor) ; Simchi, Abdolreza (Co-Advisor)
    Biopotential sensors are used in a wide range of biomedical applications. For example, measuring electric potentials on the surface of living tissues in electroencephalography (EEG), electromyography (EMG), and electrocardiography (ECG) systems in which the brain, muscle, and heart activities respectively are measured over time. Moreover, these electrodes are used in measuring the pH of different materials and also in receiving and recording the electric field changes of the environment. The major purpose of biopotential electrodes is to act as a transducer between the ionic transport of the tissue and the electron flow in the electrode. Such a transduction takes place due to an oxidation or... 

    Stiffness, Position and Orientation Optimization of the Engine Mounts to Reduce the Vibrational Noise Transmitted to the Body

    , M.Sc. Thesis Sharif University of Technology Mohaqeqi, Reza (Author) ; Nejat, Hossein (Supervisor)
    Despite the great work done in the field of the engine mount system to reduce vibrations transmitted from the vehicle to the body, an efficient process is still needed to achieve the optimal response to the design of the engine mount system.The goal of the project is to provide an ideal model for optimizing the stiffness, position, and orientation of the vehicle's engine mount system. In this regard, the activities carried out consist of three parts of the modeling, optimization, and verification of the response. In the modeling section, a linear model of 13 degrees of freedom has been proposed for the engine, mount and vehicle assembly, which also has the ability to model the rigidity of... 

    Some Applications of Singular Values Decomposition in Image Processing

    , M.Sc. Thesis Sharif University of Technology Ghobadi Ghadikalaei, Vahideh (Author) ; Mahdavi Amiri, Nezamoddin (Supervisor)
    The field of digital image processing refers to processing digital images by means of a digital computer. One of the principal applications used in digital image processing is image compression. Image compression is the problem of reducing the amount of data required to represent a digital image. The basis of the reduction process is the removal of redundant data. One of the other principal applications of image processing is noise reduction (filtering) of images corrupted with additive noise. Filtering techniques are oriented toward modeling the degradation and applying the inverse process in order to recover the original image. Image watermarking is another application of image processing.... 

    Improvement of PET Images Using Wavelet Method and its Comparison with Usual Clinical Method

    , M.Sc. Thesis Sharif University of Technology Mohammadi, Mohammad Sadegh (Author) ; Hosseini, Abolfazl (Supervisor)
    Positron emission tomography (PET) imaging is a cross-sectional imaging method in nuclear medicine. In recent years, there have been increasing interest in this method.PET imaging is very sensitive and the presence of noise in the results decreases the the image quality and precision of detection. Thus it is critical to to investigate noise in PET systems with noisy images, since it could decrease the system’s ability to detect tumors. The common method to decrease noise in nuclear medicine images is the Fourier transform (FT). The method has many applications in image processing and analysis. However, in the FT method, information regarding time and position are lost in the frequency... 

    Wavelet based speech enhancement using a new thresholding algorithm

    , Article 2004 International Symposium on Intelligent Multimedia, Video and Speech Processing, ISIMP 2004, Hong Kong, China, 20 October 2004 through 22 October 2004 ; 2004 , Pages 238-241 ; 0780386884 (ISBN) Ayat, S ; Manzuri, M. T ; Dianat, R ; Sharif University of Technology
    The Wavelet based speech enhancement is considered. In this method, the noisy signal transfers to wavelet domain. Then with applying a thresholding algorithm, the wavelet coefficients will be improved. At last using the inverse wavelet transform the enhanced signal will be obtained. In this paper, we have presented a new method for thresholding algorithm. We compared our algorithm with some of the most popular methods by several experimental tests. Both subjective and objective tests show better performance and achievements  

    An enhanced dynamic range low-power delta-sigma modulator for portable voice band applications

    , Article 2003 Southwest Symposium on Mixed-Signal Design, SSMSD 2003, 23 February 2003 through 25 February 2003 ; 2003 , Pages 263-268 ; 0780377788 (ISBN); 9780780377783 (ISBN) Safarian, A. Q ; Aslanzadeh, H. A ; Mehrmanesh, S ; Vahidfar, M. B ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    A new second order sigma delta modulator with the reduced number of op-amps, to decrease static power consumption and area, is presented for voice band applications such as codecs. This switched capacitor modulator uses reused capacitor technique to reduce the input thermal noise and circuit area. It improves the DR of modulator by almost 0.5 bit. The modulator shows 87 dB DR for voice band while consuming 125 μW from a 2.5 V supply. © 2003 IEEE  

    Toward naturalness in narrow-band speech compression

    , Article 2000 IEEE Internatinal Conference on Multimedia and Expo (ICME 2000), New York, NY, 30 July 2000 through 2 August 2000 ; Issue I/MONDAY , 2000 , Pages 440-443 Ghaemmaghami, S ; Sharif University of Technology
    This paper addresses a new mixed model for characterizing LPC excitation on a 3-band basis through analyzing harmonic structure of the residual signal. In addition, a sub-frame based analysis is developed for detecting both aperiodic pulses and noisy signals, which plays a major role in reduction of perceptual errors introduced by some certain consonants. Preliminary results show that near natural speech is achieved at 1050 bps, allocated to the excitation parameters, suggesting superiority of the proposed coding scheme to the MELP-2400 coding standard, in the sense of perceptual quality of reconstructed speech  

    Noise reduction using multi-channel FIR warped wiener filter

    , Article 13th International Multi-Conference on Systems, Signals and Devices, SSD 2016, 21 March 2016 through 24 March 2016 ; 2016 , Pages 531-536 ; 9781509012916 (ISBN) Shamsa, A ; Ghorshi, S ; Joorabchi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Enhancing the speech quality is the aim of noise reduction techniques. In order to have a desirable speech signal, it is necessary to eliminate the hearing fatigue and enhance the quality and intelligibility of speech signal. The present of additive noise causes the signal to degrade where the noise reduction techniques intend to remove the effect of noise on speech signals. However, removing the noise should not harm the speech signal when the signal is going to be heard. In this regard, Wiener filter can be used to promote the quality and intelligibility of the noisy signals. This paper explores the performance of multi-channel Wiener filter accompanied by Warped FIR filter