Knowledge Based Approach To Speech Recognition

This paper presents a knowledge/rule based approach to continuous speech recognition. The proposed recognition system (Samouelian, 1994) uses a data driven methodology, where the knowledge about the structure and characteristics of the speech signal is captured explicitly from the database by the use of inductive inference (C4.5) (Quinlan, 1986). This allows the integration of features from existing signal processing techniques, that are currently used in HMM stochastic modelling, and acoustic-phonetic features, which have been the cornerstone of traditional knowledge based techniques. Phoneme recognition results on the phonetic classes of plosives, semivowels and nasals for a combination of feature sets, for speaker dependent and independent recognition, are presented. INTRODUCTION The use of the knowledge/rule based approach to continuous speech recognition has been proposed by several researchers and applied to speech recognition (De Mori & Lam, 1986; Aikawa, 1986; Bulot & Nocera, 1..

Experimental approach of lessivage: Quantification and mechanisms

International audienceLessivage, also called argilluviation, consists of a substantial vertical transfer of particles less than 2 pm from a superficial departure horizon to a deeper horizon. This process is common in many soil types and responsible for the development of a textural differentiation in soil profiles in the subsurface. However, the mechanisms of lessivage are still poorly understood, and to our knowledge, lessivage has rarely been quantified. We propose here two original experiments of in vitro pedogenesis on soil columns to analyse the mechanisms acting in eluviation and illuviation, the two phases of lessivage, and to quantify these two phases in terms of particle export and fixation. We paid special attention to the experimental conditions, so that the conditions were favourable for lessivage and as close as possible to field conditions. The eluviation experiment showed that the release of particles was not the determining process for lessivage. We also showed that the smectite selectivity of eluviation was not continuous overtime. Both physical and chemical processes were identified as acting on both eluviation and illuviation. Concerning illuviation, experiments showed that from 25 to 90% of the eluviated particles were retained in the deeper horizon. Although large, to our knowledge this range represents the first quantification of illuviation. (C) 2013 Elsevier B.V. All rights reserved

Assessing the usage potential of SoilGen2 to predict clay translocation under forest and agricultural land uses

Long-term impacts of climate evolution and agricultural management on soil properties and thus soil functioning must be assessed by modelling studies. We focus on modelling of the clay depth distribution as a result of natural soil formation and agricultural management by using the soil genesis model SoilGen2 with loess-derived Luvisols in northern France. An essential first step is the calibration of the processes concerning clay leaching (lessivage) in this model, for which we propose a reproducible method consisting of a screening for a realistic parameter range, a sensitivity analysis and finally a model calibration. To be able to separate the effects of natural soil evolution and more recent agricultural activities, we calibrated the model firstly on natural soils still under forest. Four parameters were the most sensitive and in need of calibration, representing the volume fraction of the soil in contact with macropores, a filter coefficient and physical weathering producing clay-sized particles. These parameters were successfully calibrated, but independent validations at Belgian and Norwegian sites with Albeluvisols and Stagnosols developed in loess and marine clay did not always show an improvement on earlier calibrations. This can be related to several factors, most importantly the dominance of processes other than lessivage in Albeluvisols and uncertain reconstructions of the climate. After calibration, a functional sensitivity analysis was carried out to assess the effect of agricultural management on lessivage. Clear effects on clay loss in the topsoil were found for the length of the crop-cover period and the ploughing depth and to a lesser extent for the intensity of soil mixing and the interception evaporation of the crops. As it is not feasible to reconstruct these factors for the entire period of agriculture in this region (several millennia), further analysis should take the form of scenario studies, but this should be preceded by use of field leaching experiments to calibrate SoilGen2 over short time-scales

Contrasting soil property patterns between ditch bed and neighbouring field profiles evidence the need of specific approaches when assessing water and pesticide fate in farmed landscapes

Farm ditch networks, infrastructures designed to regulate excess water in cropped landscapes, constitute pesticide dispersal pathways or buffer zones, depending on their soil properties. Despite the key role that ditch soils play in the regulation of water and pesticide fate, their properties, especially in intermittently flooded ditches, remain poorly characterized. Therefore, our aim was to evaluate the specificity of ditch material properties to determine whether ditches require an approach that differs from that of field soils when studying water and pesticide fate in farmed landscapes. We thus analysed the variations in the pedological, herbicide sorption and flow properties of soil materials along a 2D cross-section of an intermittently flooded ditch in the Roujan catchment of southern France. We found that the upper part of the ditch bed soil profile is composed of 3 horizons that formed after the original creation of the ditch, most likely via the deposition of field-eroded particles and the accumulation of organic matter. These specific horizons have greater porosity, mostly due to their dense root systems, and contain up to 2 times more organic carbon than the neighbouring banks or field soils. Consequently, the hydraulic conductivity is greater, and the sorption of hydrophobic herbicides is up to 2 times greater in ditch bed materials than it is in soils located farther away from the ditch surface. Moreover, significant macroporal flow was evidenced in both profiles but with different contribution to the global flow. The contrasts in the hydrodynamic and sorption properties between both the ditch bed and banks materials likely results in significantly different water and pesticide infiltration patterns in ditches compared to crop fields. Given these differences, we recommend investigating the specific properties of ditch beds when studying and modelling water and pesticide fate in croplands