Sharif Digital Repository

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 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  

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... 

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... 

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 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  

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  

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... 

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... 

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  

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  

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  

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