SVMs for Automatic Speech Recognition: a Survey

Hidden Markov Models (HMMs) are, undoubtedly, the most employed core technique for Automatic Speech Recognition (ASR). Nevertheless, we are still far from achieving high-performance ASR systems. Some alternative approaches, most of them based on Artificial Neural Networks (ANNs), were proposed during the late eighties and early nineties. Some of them tackled the ASR problem using predictive ANNs, while others proposed hybrid HMM/ANN systems. However, despite some achievements, nowadays, the preponderance of Markov Models is a fact. During the last decade, however, a new tool appeared in the field of machine learning that has proved to be able to cope with hard classification problems in several fields of application: the Support Vector Machines (SVMs). The SVMs are effective discriminative classifiers with several outstanding characteristics, namely: their solution is that with maximum margin; they are capable to deal with samples of a very higher dimensionality; and their convergence to the minimum of the associated cost function is guaranteed. These characteristics have made SVMs very popular and successful. In this chapter we discuss their strengths and weakness in the ASR context and make a review of the current state-of-the-art techniques. We organize the contributions in two parts: isolated-word recognition and continuous speech recognition. Within the first part we review several techniques to produce the fixed-dimension vectors needed for original SVMs. Afterwards we explore more sophisticated techniques based on the use of kernels capable to deal with sequences of different length. Among them is the DTAK kernel, simple and effective, which rescues an old technique of speech recognition: Dynamic Time Warping (DTW). Within the second part, we describe some recent approaches to tackle more complex tasks like connected digit recognition or continuous speech recognition using SVMs. Finally we draw some conclusions and outline several ongoing lines of research

A direct method for analyzing the nonlinear vehicle–structure interaction

This article presents an accurate, efficient and stable algorithm to analyze the nonlinear vertical vehicle-structure interaction. The governing equilibrium equations of the vehicle and structure are complemented with additional constraint equations that relate the displacements of the vehicle with the corresponding displacements of the structure. These equations form a single system, with displacements and contact forces as unknowns, that is solved using an optimized block factorization algorithm. Due to the nonlinear nature of contact, an incremental formulation based on the Newton method is adopted. The vehicles, track and structure are modeled using finite elements to take into account all the significant deformations. The numerical example presented clearly demonstrates the accuracy and computational efficiency of the proposed method

SITUACIONES DE LAS PRÁCTICAS CLÍNICAS QUE PROVOCAN ESTRÉS EN LOS ESTUDIANTES DE ENFERMERÍA

Observacional, cross-sectional comparative study given to the 3 courses students of infirmary registered in course 2004-05 in the School of Meixoeiro (Vigo), with the objective to valuate situations of the clinical practices, grouped by factors, are but more stressant for the students. The Kezkak and Stai questionnaires have been used to make. Participation in the study has been of the 85.30%. with a rank of ages between 19-41 years. The obtained average scores in our school reflect a high score in almost all the items considered like leading factors of stress, in comparison with the students of other studies. When making the correlation between anxiety characteristic, anxiety state and the situations , we have found significant between some of the factors and anxiety state, but not in anxiety characteristic, which seem to indicate that the stress situations that arelived with greater intensity are more related to the insecurity than with a characteristic of its character. As a measure to improve the level of anxiety of our students in the accomplishment of its clinical practices we propose interventions that facilitate the education of relaxation techniques and facing facts.Estudio observacional, transversal comparativo, realizado a los alumnos de los tres cursos de enfermería matriculados en el curso 2004-05 en la Escuela do Meixoeiro (Vigo), con el objetivo de valorar qué situaciones de las prácticas clínicas, agrupadas por factores, resultan más estresantes para los/las estudiantes. La medición se ha realizado con los cuestionarios Kezkak y Stai. La participación en el estudio ha sido del 85,30%, con un rango de edad entre 19-41 años. Las puntuaciones medias obtenidas en nuestra Escuela reflejan una puntuación alta en casi todos los ítems considerados como factores desencadenantes de estrés, en comparación con los alumnos de otros estudios. Al realizar la correlación entre ansiedad rasgo, ansiedad estado y las situaciones estresantes, hemos encontrado significación entre algunos de los factores y la ansiedad estado, pero no en la ansiedad rasgo, lo que parece indicar que las situaciones de estrés que viven con mayor intensidad están más relacionadas con la inseguridad que con un rasgo de su carácter. Como medida para mejorar el nivel de ansiedad de nuestros alumnos en la realización de sus prácticas clínicas proponemos intervenciones que faciliten la enseñanza de técnicas de relajación y afrontamiento

Robust ASR using Support Vector Machines

The improved theoretical properties of Support Vector Machines with respect to other machine learning alternatives due to their max-margin training paradigm have led us to suggest them as a good technique for robust speech recognition. However, important shortcomings have had to be circumvented, the most important being the normalisation of the time duration of different realisations of the acoustic speech units. In this paper, we have compared two approaches in noisy environments: first, a hybrid HMM–SVM solution where a fixed number of frames is selected by means of an HMM segmentation and second, a normalisation kernel called Dynamic Time Alignment Kernel (DTAK) first introduced in Shimodaira et al. [Shimodaira, H., Noma, K., Nakai, M., Sagayama, S., 2001. Support vector machine with dynamic time-alignment kernel for speech recognition. In: Proc. Eurospeech, Aalborg, Denmark, pp. 1841–1844] and based on DTW (Dynamic Time Warping). Special attention has been paid to the adaptation of both alternatives to noisy environments, comparing two types of parameterisations and performing suitable feature normalisation operations. The results show that the DTA Kernel provides important advantages over the baseline HMM system in medium to bad noise conditions, also outperforming the results of the hybrid system.Publicad

Middle Neolithic farming of open-air sites in SE France: new insights from archaeobotanical investigations of three wells found at Les Bagnoles (L'Isle-sur-la-Sorgue, Dépt. Vaucluse, France)

Previous reviews of Middle Neolithic agricultural practice (4400–3500 cal bc) in southern France have highlighted a change in crop assemblages after 4000 cal bc, with a reduction of naked wheat and an increase of emmer and partly of einkorn. The recent investigation of three wells from the site of Les Bagnoles (4250–3800 cal bc) in the periphery of the southern Rhône valley yielded an unprecedented amount of waterlogged uncharred and charred plant macro remains that offer new insights into crop diversity and its changes over time. The results from the wells at Les Bagnoles were compared with other dated sunken features from open-air sites (in contrast to caves and rock shelters), with the aim of identifying patterns sug-gesting changes in the crop spectra between the early (MN1) and late (MN2) Middle Neolithic phases from taphonomically comparable contexts. The results from Les Bagnoles demonstrate that oil crops and pulses are underrepresented in dry sites and that they were a significant part of Middle Neolithic agriculture. They also indicate an increase in the representation of einkorn (instead of emmer) during MN2 that is also visible in other open-air sites. The comparison of the archaeobotani-cal results with silo storage capacity values as a proxy for average production capacity per household leads us to propose a possible drop in naked wheat productivity and opens new questions in factors affecting crop choice at the beginning of the 4th millennium cal bc

Intermediate Band Solar Cell with Extreme Broadband Spectrum Quantum Efficiency

We report, for the first time, about an intermediate band solar cell implemented with InAs/AlGaAs quantum dots whose photoresponse expands from 250 to ~ 6000  nm. To our knowledge, this is the broadest quantum efficiency reported to date for a solar cell and demonstrates that the intermediate band solar cell is capable of producing photocurrent when illuminated with photons whose energy equals the energy of the lowest band gap. We show experimental evidence indicating that this result is in agreement with the theory of the intermediate band solar cell, according to which the generation recombination between the intermediate band and the valence band makes this photocurrent detectable