Wavelets and LPG-PCA for Image Denoising

In this chapter, a new image denoising approach is proposed. It combines two image denoising techniques. The first one is based on a wavelet transform (WT), and the second one is a two-stage image denoising by PCA (principal component analysis) with LPG (local pixel grouping). In this proposed approach, we first apply the first technique to the noisy image in order to obtain the first estimation version of the clean image. Then, we estimate the noise-level from the noisy image. This estimate is obtained by applying the third technique of noise estimation from noisy images. The third step of the proposed approach consists in using the first estimation of the clean image, the noisy image, and the estimate of the noise-level as inputs of the second image denoising system (LPG-PCA). A comparative study of the proposed technique and the two others denoising technique (one is based on WT and and the second is based on LPG-PCA), is performed. This comparative study used a number of noisy images, and the obtained results from PSNR (peak signal-to-noise ratio) and SSIM (structural similarity) computations show that the proposed approach outperforms the two other denoising approaches (the first one is based on WT and the second one is based on LPG-PCA)

Perspective Chapter: New Image Denoising Approach Based on SWT and 2-D Dual-Tree Discrete Wavelet Transform

In this chapter, we propose a new image denoising approach. It consists in applying a Stationary Wavelet Transform (SWT) based image denoising technique, in the domain of 2‐D Dual-Tree Discrete Wavelet Transform. In fact, this proposed approach consists first of applying the 2‐D Dual-Tree Discrete Wavelet Transform to the noisy image. Then, the obtained noisy wavelet coefficients are denoised by applying to each of them a SWTbased image denoising technique. Finally, the denoised image is reconstructed by applying the inverse of the 2‐D Dual-Tree Discrete Wavelet Transform to the obtained denoised wavelet coefficients. For applying this SWT based image denoising technique, we use soft thresholding, the Daubechies 4 as the mother wavelet and the decomposion level is equal to 5. The performance of this proposed image denoising approach, is pouved by the results obtained from the computations of PSNR (Peak Signal-to-Noise Ratio) and SSIM (Structural Similarity)

Un système de formation à l’enseignement des sciences dans le contexte éducatif marocain : des conditions pour une évolution possible

Des enjeux et des problématiques actuels et futurs vont constituer des facteurs puissants de changement, de modulation et de régulation des modes de pensées, des modes de consommation, et des relations interpersonnelles et intercommunautaires. Une évolution parallèle devrait concerner le système de la formation, plus particulièrement la formation à l’enseignement des sciences. Cependant, par incompétence ou par peur de transgresser les règles établies, dictées par les programmes officiels de formation, la majorité des formateurs perpétuent une tradition de formation et adopteraient exceptionnellement une posture critique par rapport à leurs pratiques de formation. Le système de formation à l’enseignement des sciences au Maroc ne semble pas évoluer en dépit des intentions de réforme manifestées concernant l’amélioration de l’enseignement des sciences. Ce texte relate quelques obstacles et des conditions d'une évolution possible du système de formation à l'enseignement des sciences de la vie et de la terre au Maroc. En fait, cet article essaye d’articuler deux questions principales à savoir les obstacles à l’évolution du système de formation à l’enseignement des sciences et celle relative aux conditions de possibilité de la conception, d’élaboration et de la mise en œuvre de nouveaux modules de formation relativement à l'enseignement des sciences de la vie et de la terre.Stakes and problems, current and future, are going to establish powerful factors of change, modulation and regulation of the ways of thinking, the modes of consumption, and intrapersonal and intercommunity relationship. A parallel evolution should concern the formation system, more particularly the formation or training in the teaching of sciences. However, by incompetence or by fear of breaking established rules dictated by the official programs of the formation, some trainers perpetuate the formation tradition and would exceptionally adopt a critical posture, with regard to their practices of formation. In the teaching of sciences in Morocco, the formation system does not seem to evolve, in spite of intended reforms in the field. The present study deals with obstacles and possible conditions of an evolution of the formation in the education of life and earth sciences, in Morocco. In fact, this article tries to articulate two main questions, on the one hand, to know obstacles to the evolution of the system of training in the education of sciences, and on the second hand, the obstacles relating to the conditions of the comprehension possibility, elaboration and the implementation of new formation modules in relation to the education of life an earth sciences

Speech Enhancement Based on LWT and Artificial Neural Network and Using MMSE Estimate of Spectral Amplitude

In this chapter, we will detail a new speech enhancement technique based on Lifting Wavelet Transform (LWT) and Artifitial Neural Network (ANN). This technique also uses the MMSE Estimate of Spectral Amplitude. It consists at the first step in applying the LWTto the noisy speech signal in order to obtain two noisy details coefficients, cD1 and cD2 and one approximation coefficient, cA2. After that, cD1 and cD2 are denoised by soft thresholding and for their thresholding, we need to use suitable thresholds, thrj,1≤j≤2. Those thresholds, thrj,1≤j≤2, are determined by using an Artificial Neural Network (ANN). The soft thresholding of those coefficients, cD1 and cD2, is performed in order to obtain two denoised coefficients, cDd1 and cDd2 . Then the denoising technique based on MMSE Estimate of Spectral Amplitude is applied to the noisy approximation cA2 in order to obtain a denoised coefficient, cAd2. Finally, the enhanced speech signal is obtained from the application of the inverse of LWT, LWT−1 to cDd1, cDd2 and cAd2. The performance of the proposed speech enhancement technique is justified by the computations of the Signal to Noise Ratio (SNR), Segmental SNR (SSNR) and Perceptual Evaluation of Speech Quality (PESQ)

BionicWavelet Based Denoising Using Source Separation

We consider the problem of speech denoising using source separation. In this study we have proposed a hybrid technique that consists in applying in the first step, the Bionic Wavelet Transform (BWT) to two different mixtures of the same speech signal with noise. This speech signal is corrupted by a Gaussian white noise with two different values of the Signal to Noise Ratio (SNR) in order to obtain those two mixtures. The second step consists in computing the entropy of each bionic wavelet coefficient and finds the two subbands having the minimal entropy. Those two subbands are used to estimate the separation matrix of the speech signal from noise by using the source separation. Our proposed technique is evaluated by comparing it to the denoising technique based on source separation in time domain

Difficultés De Mise En Œuvre De La Continuité Didactique Mathématique-Mécanique Au Secondaire Collégial, Registre Sémiotique Et Transfert Comme Éléments D’analyse

This article deals with the numerous pedagogical and didactic constraints to the transdisciplinary knowledge transfer between mathematics and physics (mechanics) at the last year of secondary school. By taking into consideration the three entities of the didactic triangle (Content, students and teachers), we analyzed in this exploratory study official pedagogical orientations, curricula and textbooks of mathematics and physics. Then, we administered to a sample of 12 to 15-year-old pupils, mathematical and physical written questionnaires in which they have to use proportionality/linearity concept by considering different register of semiotic representation and the rationality frame of each discipline., the analysis of the results reveal some difficulties that can be explained by a lack of knowledge related to the change of rationality frame and semiotic register rules. In order to understand the origin of these difficulties, we proceeded by analyzing the transdisciplinary practices of mathematics/physics teachers by means of a written semi-open questionnaire whose results highlight interdidactic rupture between mathematics and physics. To remedy that, we propose some strategies and possible lines of actions

Didactic use of the history of science in the context of teaching of science

L'article vise à présenter la conception, l'élaboration et la mise en oeuvre d'un module de formation structuré à partir d'éléments d'histoire des sciences. Des faits historiques ont servi à dégager des implications didactiques misent à profit dans une optique de formation à l'enseignement des sciences. Cet article rend compte également d'une appréciation sommaire des retombées de ce module de formation après la deuxième année de sa mise en oeuvre