Speech enhancement with spectral magnitude side information

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 43-44).by Charles Kasimer Sestok, IV.S.M

Speech coding at medium bit rates using analysis by synthesis techniques

Speech coding at medium bit rates using analysis by synthesis technique

Perceptual models in speech quality assessment and coding

The ever-increasing demand for good communications/toll quality speech has created a renewed interest into the perceptual impact of rate compression. Two general areas are investigated in this work, namely speech quality assessment and speech coding. In the field of speech quality assessment, a model is developed which simulates the processing stages of the peripheral auditory system. At the output of the model a "running" auditory spectrum is obtained. This represents the auditory (spectral) equivalent of any acoustic sound such as speech. Auditory spectra from coded speech segments serve as inputs to a second model. This model simulates the information centre in the brain which performs the speech quality assessment. [Continues.

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Development of O,N-bidentate ruthenium catalysts for isomerization and kinetic studies of ruthenium carbenes for C=C coupling reactions

The fountainhead to develop the chemical science is the demand of various compounds by human being. While most of the requirements concerns organic molecules, organometallic compounds have paved the way of homogeneous catalysis in producing bulk, fine chemicals, and even natural products. During the last decade, ruthenium catalysts have provided new indispensable synthetic methods that cannot be promoted by other catalysts and applied in wide range of chemical reactions. This work deals with the development of O,N-bidentate ruthenium homogeneous catalysts for isomerization and kinetic studies of ruthenium cabenes for C=C coupling reactions. Specifically designed ligands are the key in optimizing the efficiency of catalysts. Schiff bases are known to strongly enhance the thermal and moisture stability of the corresponding complexes and isomerization is important in many chemical processes. The above reasons promote the first part of the work to concentrate on the synthesis of a novel class of homogeneous ruthenium complexes containing Schiff bases as O,N-bidentate ligands catalyzing the isomerization reaction. By a proper choice of the Schiff base, the new ruthenium complexes showed improved reactivity, selectivity and stability toward air and moisture during the isomerization reaction. The temperature and solvent tolerance was likewise substantially improved. Later, another series of analogue Schiff bases ruthenium complexes has been synthesized as isomerization catalysts and showed even better reactivity, selectivity and stability. The formation of carbon-carbon bonds is one of the most fundamental chemical processes. In this context, C=C coupling reactions (metathesis, cyclopropanation and etc.) make a significant contribution. Despite the recent advances, the search for commercially relevant catalyst systems remains challenging. The kinetic studies of ruthenium carbenes are useful for fundamental insight to design new catalysts or to improve existing catalytic systems. The second part of this work estabilished a pre-research for the future outlook

Efficient Hybrid Virtual Room Acoustic Modelling

This thesis investigates approaches to virtual room acoustic modelling and auralisation in order to a develop hybrid modelling solution that is capable of efficient and accurate simulation of enclosed sound propagation. Emphasis is placed on the advantages and disadvantages of state of the art numerical and geometric acoustic modelling methods. Numerical methods have been shown to preserve important sound wave characteristics such as diffraction and room modes, and are considered more accurate for low frequency acoustic modelling than geometric techniques which fail to preserve such wave effects. However, the implementation of numerical acoustic models inherently requires large computational effort compared to more efficient geometric techniques such as ray-tracing. This is particularly problematic for simulations of large-scale 3D acoustic environments and for high spatio-temporal sampling rates. A novel acoustic modelling solution is presented, which seeks to circumvent the disadvantageous computational requirements of 3D numerical models while producing a suitable approximation to low frequency sound behaviour. This modelling technique incorporates multiple planar cross-sectional 2D Finite Difference schemes that are utilised in combination to synthesise low frequency wave propagation throughout the target acoustic field. In this way a subset of prominent low frequency sound wave characteristics may be emulated with low computational cost compared to 3D numerical schemes. These low-frequency results can then be combined with the high-frequency output from efficient geometric simulations to create a hybrid model providing accurate broadband results at a relatively low computational cost. Investigation of room impulse response rendering for a series of theoretic and real spaces demonstrates advantages of this new hybrid acoustic modelling technique over purely ray-based methods in terms of low frequency accuracy, and over 3D numerical methods in terms of computational efficiency. Conclusions are drawn from objective measurements obtained from simulation results of the virtual models produced. Results demonstrate the applicability of the novel hybrid approach to the enhancement of purely ray-based room impulse response rendering by which a more realistic representation of low frequency wave phenomena may be simulated in an efficient manner, improving the theoretical accuracy of objective and audible results. This study contributes towards research and design of high-speed, interactive virtual acoustic simulations appropriate for industrial and creative virtual reality applications

Engineering the electrochromism and ion conduction of layer-by-layer assembled films

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2003.Includes bibliographical references.This work applies the processing technique of layer-by-layer (LBL) assembly to the creation and development of new electrochemically active materials. Elements of the thin-film electrochromic cell were chosen as a particular focus for LBL fabrication. Layer-by-layer assembly is the ideal processing tool to tailor the electrochemical systems within electrochromic cells because modulating processing conditions can greatly impact the nanoscale composition and morphology of the resultant films. For the first time, this control was used to: 1) intelligently design electrochromic LBL assembled composite films that facilitated ion motion for faster switching and exhibited enhanced or shifted coloration, 2) combine multiple electrochromic materials into novel LBL assembled composites with even higher contrast, faster switching, and multiple colored states, and finally 3) develop and optimize several LBL assembled polymer electrolyte films that display high ionic conductivity and sound mechanical integrity. Electrochromic cell elements were chosen not only for their undeveloped commercial potential, but also because they incorporate multifunctional material systems with alternative applications. Studies of LBL fabrication and the operation of electrochromic cells provide insight into intermolecular interactions, internal and external film interfaces, thin film electrochemistry, and charged species mobility in polymer solids. First investigated was the capability of LBL assembly to alter the properties of electrochromic films by varying molecular blending.(cont.) The electrochromophores for this investigation were appropriated from all corners of the materials spectrum, including discrete electrochromic polymers, conjugated polymers, soft colloidal suspensions, and inorganic particle dispersions. In each system, the influence of assembly conditions and film composition was elucidated; in particular systems the hydrophobicity, acidity, and morphology of the films were found to impact the electrochemistry and optical character of the films, providing a means to modulate these properties by directing LBL assembly design choices. Because of the high uniformity and thickness control allowed by LBL assembly, the contrast and switching performance of all LBL assembled electrochromic films were in general superior to those of films containing the same electrochromophores fabricated by other methods. One particularly promising system involved novel LBL assembled films containing the same electrochromophores fabricated by other methods. One particularly promising system involved novel LBL assembled films containing electrochromic metal hexacyanoferrate nanocrystals of the Prussian blue family. These films displayed fast and deep coloration; synthetic nanocrystal variation extended absorbance over a broad spectral range so that these inorganic/polymer composite films could potentially be considered as elements in a full-color switchable CMYK display. The power of the LBL assembly technique was leveraged further with the successful fabrication of "dual electrochrome" electrodes ...by Dean M. DeLongchamp.Ph.D

Valorization of Bio-Alcohols into Added Value Chemicals

[ES] El presente trabajo de investigación está centrado en la valorización y la mejora del bioetanol, empleando catalizadores heterogéneos, en un reactor de flujo continuo a escala de laboratorio. En primer lugar, en los laboratorios del Departamento de Química Industrial de la Universidad de Bolonia (Unibo), se ha estudiado la conversión catalítica del etanol en fase gaseosa sobre catalizadores basados en hidroxiapatitas (HAP). Los ensayos catalíticos se llevaron a cabo alimentando un reactor de lecho fijo a escala de laboratorio, empleando el catalizador en forma de pellets y una mezcla de etanol/He, en el rango de temperatura de 300-600 ºC. El interés se focalizó en la formación de productos de alta condensación, con el fin de obtener una mezcla orgánica que pueda ser empleada como bio-combustible. Tras seleccionar las condiciones de reacción, se sintetizaron y probaron diferentes hidroxiapatitas con capacidad de intercambio iónico que poseen metales de transición (Fe, Cu) y metales alcalinotérreos (Sr) en su composición. Mientras que las HAP conteniendo metales de transición actúan esencialmente como catalizadores ácidos, produciendo principalmente el producto de la deshidratación del etanol, el etileno, el catalizador de Sr-HAP permite la formación de una mezcla de reacción compleja, la cual necesita de una mayor optimización para cumplir con los requisitos adecuados para su posterior empleo como biofuel. A continuación, en los laboratorios del Instituto de Tecnología Química (ITQ) de la Universidad Politécnica de Valencia (UPV), el estudio se centró en dos materiales catalíticos diferentes, el óxido de zirconio y la sepiolita, una arcilla natural abundante en España. Ambos materiales se han probados para la transformación de etanol, en el rango de temperatura de 300-450 ºC, empleando un reactor de lecho fijo a escala laboratorio, con el catalizador en forma de pellets, y usando una mezcla de etanol/N2. Los catalizadores con óxido de zirconio se prepararon mediante dos métodos diferentes, precipitación e hidrotermal, variando algunos de los parámetros de síntesis (pH, naturaleza de la base), y empleando algunos metales de transición como elementos dopantes (Ti, Y). La presencia de un elemento dopante en la estructura de la zirconia favorece la estabilización de las fases tetragonal y cúbica frente a fase monoclínica. Todas las muestras exhibieron un comportamiento ácido. Resulta interesante que la zirconia dopada con 5%mol de Ti exhibe un comportamiento catalítico diferente, produciendo el dietiléter como principal producto a 300ºC, mientras que los otros catalizadores producen principalmente etileno, ambos, productos de la deshidratación del etanol. Por otra parte, se ha estudiado el efecto de las propiedades ácido-base de la sepiolita, modificada con metales alcalinos (Na, K, Cs) y cargas de metal variables (2, 4, 5, 7, 14 wt%), y de las propiedades redox de la sepiolita, como soporte de CuO o NiO, sobre la conversión catalítica de etanol a n-butanol. Las sepiolitas tratadas térmicamente actúan principalmente como catalizadores ácidos, produciendo preferentemente productos de deshidratación del etanol (etileno y dietiléter). Mientras que la presencia de un metal de transición no favorece la producción de n-butanol, la presencia de un metal alcalino en el sistema catalítico parece ser crucial para la formación de n-butanol. Los mejores resultados en términos de actividad (conversión de etanol, 59%) y selectividad (30%) de n-butanol se han obtenido a 400 ºC y un tiempo de contacto, W/F, de 2 g/mL·s, con el catalizador basado en sepiolita calcinada a 500 ºC, y modificada con 7 wt% de cesio, mediante impregnación en fase acuosa.[CA] El present treball de recerca està centrat en la valorització i la millora del bioetanol, emprant catalitzadors heterogenis, en un reactor de flux continu a escala de laboratori. En primer lloc, en els laboratoris del Departament de Química Industrial de la Universitat de Bolonya (Unibo), s'ha estudiat la conversió catalítica de l'etanol en fase gasosa sobre catalitzadors basats en hidroxiapatitas (HAP). Els assajos catalítics es van dur a terme alimentant un reactor de llit fix, a escala de laboratori, contenint el catalitzador en forma de pèl·lets amb una mescla d'etanol/He, en el rang de temperatura de 300-600 °C. L'interés es va focalitzar en la formació de productes d'alta condensació, amb la finalitat d'obtindre una mescla orgànica que puga ser emprada com a bio-combustible. Després de seleccionar les condicions de reacció, es van sintetitzar i van provar diferents hidroxiapatitas amb capacitat d'intercanvi iònic que posseeixen metalls de transició (Fe, Cu) i metalls alcalinotérreos (Sr) en la seua composició. Mentre que les HAP contenint metalls de transició actuen essencialment com a catalitzadors àcids produint principalment el producte de la deshidratació de l'etanol, l'etilé, el catalitzador de Sr-HAP permet la formació d'una mescla de reacció complexa, la qual necessita d'una major optimització per a complir amb els requisits adequats per a la seua posterior ocupació com biofuel. A continuació, en els laboratoris de l'Institut de Tecnologia Química (ITQ) de la Universitat Politècnica de València (UPV), l'estudi es va centrar en dos materials catalítics diferents, l'òxid de zirconio i sepiolita, una argila natural abundant a Espanya. Tots dos materials s'han provats per a la transformació d'etanol en el rang de temperatura de 300-450 °C, emprant un reactor de llit fix a escala laboratori, contenint el catalitzador en forma de pèl·lets, i usant una mescla d'etanol/N2 Els catalitzadors amb òxid de zirconio es van preparar mitjançant dos mètodes diferents, precipitació i hidrotermal, variant alguns dels paràmetres de síntesis (pH, naturalesa de la base), i emprant alguns metalls de transició com a elements dopants (Ti, Y). La presència d'un element dopant en l'estructura de la zircònia afavoreix l'estabilització de les fases tetragonal i cúbica enfront de fase monoclínica Totes les mostres van exhibir un comportament àcid. Resulta interessant que la zircònia dopada amb 5%mol de Ti exhibisca un comportament catalític diferent, produint el dietiléter com a principal producte a 300 °C, mentre que les altres mostres produeixen principalment etilé, tots dos, productes de la deshidratació de l'etanol. D'altra banda s'ha estudiat l'efecte de les propietats àcid-base de la sepiolita, modificada amb metalls alcalins (Na, K, Cs) i càrregues de metall variables (2, 4, 5, 7, 14 wt%), i de les propietats redox de la sepiolita, com a suport de CuO o NiO, sobre la conversió catalítica d'etanol a n-butanol. Les sepiolites tractades tèrmicament actuen principalment com a catalitzadors àcids, produint principalment productes de deshidratació de l'etanol (etilé i dietiléter). Mentre que la presència d'un metall de transició no afavoreix la producció de n-butanol, la presència d'un metall alcalí en el sistema catalític sembla ser crucial per a la formació del n-butanol. Els millors resultats en termes d'activitat (conversió d'etanol, 59%) i selectivitat (30%) de n-butanol s'han obtingut a 400°C i un temps de contacte, W/F, de 2 g/ml·s amb el catalitzador compost de sepiolita calcinada a 500 °C, i modificada amb 7 wt% de Cs.[EN] The present research work focused on the valorisation and upgrading of bio-ethanol over heterogeneous catalysts in a lab-scale continuous gas-flow system. Firstly, in the laboratories of the Department of Industrial Chemistry of the University of Bologna (Unibo), the catalytic ethanol gas-phase conversion was studied over hydroxyapatite (HAP) based catalysts. Catalytic tests have been carried out in the temperature range 300-600°C by feeding an ethanol/He mixture into a quartz lab-scale fixed bed reactor of pelletized catalyst. The focus was placed on enhancing the formation of higher condensation products in order to obtain an organic mixture with application as bio-fuel. After choosing the reaction conditions, ion-exchanged hydroxyapatite with transition metals (i.e., Fe, Cu) and alkaline earth metal (i.e., Sr) have been synthesized and tested. While the transition metal-exchanged HAP acted essentially as acid catalysts, yielding mainly the dehydration product of ethanol, ethylene, the Sr-HAP catalyst led to the formation of a complex reaction mixture the composition of which need further optimization in order to fill the requisite to be used as fuel-blend. Then, in the laboratories of the Institute of Chemical Technology (ITQ) of the Polytechnic University of Valencia (UPV), the study focused on two different catalytic materials, zirconium oxide and the natural clay sepiolite. Both the materials have been tested into the ethanol transformation carrying out the catalytic tests in the temperature range 300-450 °C by feeding an ethanol/N2 mixture into a quartz lab-scale fixed bed reactor of pelletized catalyst. Zirconium-oxide based catalysts have been prepared through two different methods, precipitation and hydrothermal, by varying some synthetic parameters (i.e., pH, the nature of the base) and by adding a transition metal as dopant agent (i.e., Ti and Y). The presence of a dopant into the zirconia structure favoured the stabilization of the tetragonal or cubic phase against the monoclinic one. All samples exhibited acidic behaviour. Interestingly, 5%mol Ti-doped zirconia exhibited a different catalytic behaviour yielding diethyl ether as major product at 300°C, while all the others samples produced mainly ethylene, both dehydration products of ethanol. The effect of acid-base properties of sepiolite, using alkali metals (i.e., Na, K, Cs) with different metal loading (i.e., 2, 4, 5, 7, 14 wt%) as promoters, and of the redox properties of sepiolite-supported CuO or NiO, on the catalytic conversion of ethanol into n-butanol has been investigated. Thermal treated sepiolite samples mainly acted as acid catalyst, yielding preferentially the dehydration products of ethanol (ethylene and diethyl ether). While the presence of a transition metal did not favour n-butanol production, the presence of an alkali metal into the catalytic system appeared to be crucial for n-butanol formation. Best results in terms of activity (ethanol conversion, 59%) and n-butanol selectivity (30%) where obtained at 400ºC and a contact time, W/F, of 2 g/mL·s over the catalyst consisting of sepiolite calcined at 500ºC modified with 7 wt% of cesium.Balestra, G. (2022). Valorization of Bio-Alcohols into Added Value Chemicals [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/184991TESI

Coherent fibre-optic link: applications in Time and Frequency metrology, Geodesy, Radio Astronomy and Seismology

L'abstract è presente nell'allegato / the abstract is in the attachmen