Vulnérabilité à la chaleur dans le contexte des changements climatiques.

Thèse réalisée en cotutelle avec Université Paris 11 (Ecole Doctorale 420)

Spectral and nonlinear optical characterization of ZnO nanocomposites

The spectral and nonlinear optical characteristics of nano ZnO and its composites are investigated. The fluorescence behaviour of nano colloids of ZnO has been studied as a function of the excitation wavelength and there is a red shift in emission peak with excitation wavelength. Apart from the observation of the reported ultra violet and green emissions, our results reveal that additional blue emissions at 420 nm and 490 nm are developed with increasing particle size. Systematic studies on nano ZnO have indicated the presence of luminescence due to excitonic emissions when excited with 255 nm as well as significant contribution from surface defect states when excited with 325 nm. In the weak confinement regime, the third-order optical susceptibility χ(3) increases with increasing particle size (R) and annealing temperature (T) and a R2 and T2.5 dependence of χ(3) is obtained for nano ZnO. ZnO nanocolloids exhibit induced absorption whereas the self assembled films of ZnO exhibit saturable absorption due to saturation of linear absorption of ZnO defect states and electronic effects. ZnO nanocomposites exhibit negative nonlinear index of refraction which can be attributed to two photon absorption followed by weak free carrier absorption. The increase of the third-order nonlinearity in the composites can be attributed to the enhancement of exciton oscillator strength. The nonlinear response of ZnO nanocomposites is wavelength dependent and switching from induced absorption to saturable absorption has been observed at resonant wavelengths. Such a change-over is related to the interplay of plasmon/exciton band bleach and optical limiting mechanisms. This study is important in identifying the spectral range and the composition over which the nonlinear material acts as an optical limiter. ZnO based nanocomposites are potential materials for enhanced and tunable light emission and for the development of nonlinear optical devices with a relatively small optical limiting threshold.

Size dependent fluorescence spectroscopy of nanocolloids of ZnO

In this article we present size dependent spectroscopic observations of nanocolloids of ZnO. ZnO is reported to show two emission bands, an ultraviolet (UV) emission band and another in the green region. Apart from the known band gap 380 nm and impurity 530 nm emissions, we have found some peculiar features in the fluorescence spectra that are consistent with the nanoparticle size distribution. Results show that additional emissions at 420 and 490 nm are developed with particle size. The origin of the visible band emission is discussed. The mechanism of the luminescence suggests that UV luminescence of ZnO colloid is related to the transition from conduction band edge to valence band, and visible luminescence is caused by the transition from deep donor level to valence band due to oxygen vacancies and by the transition from conduction band to deep acceptor level due to impurities and defect states. A correlation analysis between the particle size and spectroscopic observations is also discussed.

Analysis and Optimization of Machining Process Using Evolutionary Algorithms

To ensure quality of machined products at minimum machining costs and maximum machining effectiveness, it is very important to select optimum parameters when metal cutting machine tools are employed. Traditionally, the experience of the operator plays a major role in the selection of optimum metal cutting conditions. However, attaining optimum values each time by even a skilled operator is difficult. The non-linear nature of the machining process has compelled engineers to search for more effective methods to attain optimization. The design objective preceding most engineering design activities is simply to minimize the cost of production or to maximize the production efficiency. The main aim of research work reported here is to build robust optimization algorithms by exploiting ideas that nature has to offer from its backyard and using it to solve real world optimization problems in manufacturing processes.In this thesis, after conducting an exhaustive literature review, several optimization techniques used in various manufacturing processes have been identified. The selection of optimal cutting parameters, like depth of cut, feed and speed is a very important issue for every machining process. Experiments have been designed using Taguchi technique and dry turning of SS420 has been performed on Kirlosker turn master 35 lathe. Analysis using S/N and ANOVA were performed to find the optimum level and percentage of contribution of each parameter. By using S/N analysis the optimum machining parameters from the experimentation is obtained.Optimization algorithms begin with one or more design solutions supplied by the user and then iteratively check new design solutions, relative search spaces in order to achieve the true optimum solution. A mathematical model has been developed using response surface analysis for surface roughness and the model was validated using published results from literature.Methodologies in optimization such as Simulated annealing (SA), Particle Swarm Optimization (PSO), Conventional Genetic Algorithm (CGA) and Improved Genetic Algorithm (IGA) are applied to optimize machining parameters while dry turning of SS420 material. All the above algorithms were tested for their efficiency, robustness and accuracy and observe how they often outperform conventional optimization method applied to difficult real world problems. The SA, PSO, CGA and IGA codes were developed using MATLAB. For each evolutionary algorithmic method, optimum cutting conditions are provided to achieve better surface finish.The computational results using SA clearly demonstrated that the proposed solution procedure is quite capable in solving such complicated problems effectively and efficiently. Particle Swarm Optimization (PSO) is a relatively recent heuristic search method whose mechanics are inspired by the swarming or collaborative behavior of biological populations. From the results it has been observed that PSO provides better results and also more computationally efficient.Based on the results obtained using CGA and IGA for the optimization of machining process, the proposed IGA provides better results than the conventional GA. The improved genetic algorithm incorporating a stochastic crossover technique and an artificial initial population scheme is developed to provide a faster search mechanism. Finally, a comparison among these algorithms were made for the specific example of dry turning of SS 420 material and arriving at optimum machining parameters of feed, cutting speed, depth of cut and tool nose radius for minimum surface roughness as the criterion. To summarize, the research work fills in conspicuous gaps between research prototypes and industry requirements, by simulating evolutionary procedures seen in nature that optimize its own systems.

Photoluminescence Studies Of Microwave Assisted Synthesized Zno Micro Structures

ZnO micro particles in the range 0.4-0.6 μm were synthesized by microwave irradiation method. The XRD analysis reveals that the sample is in the wurtzite phase with orientation along the (101) plane. SAED pattern of the sample reveals the single crystalline nature of the micro grains. TEM images show the formation of cylindrical shaped ZnO micro structures with hexagonal faces. The optical phonon modes were slightly shifted in the Raman spectrum,attributed to the presence of various crystalline defects and laser induced local heating at the grain boundaries. A broad transmission profile was observed in the FTIR spectrum from 1550-3400 cm-1 which falls in the atmospheric transparency window region. PL spectrum centered at 500 nm with a broad band in the region 420-570 nm comprised of different emission peaks attributed to transition between defect levels. Various emission levels in the sample were expliained with a band diagram

Biblische, mythische und fremde Frauen

In the texts and illustrations of medieval Mappae mundi, women are represented in three different roles: as biblical or Christian characters (such as Eve in the Garden of Eden, Lot's wife and female saints), as legendary or mythical figures (e.g. the Queen of Sheba, mermaids) and as 'other' creatures with a deviant behaviour from the European norm (e.g. Amazons). The principal goal of this study is to analyse the different strategies that were developed by male European observers to project a filtered image of woman in the selective medium of cartography from the tenth to the fifteenth century.

Development of hybrid UV VCSEL with organic active material and dielectric DBR mirrors for medical, sensoric and data storage applications

Lasers play an important role for medical, sensoric and data storage devices. This thesis is focused on design, technology development, fabrication and characterization of hybrid ultraviolet Vertical-Cavity Surface-Emitting Lasers (UV VCSEL) with organic laser-active material and inorganic distributed Bragg reflectors (DBR). Multilayer structures with different layer thicknesses, refractive indices and absorption coefficients of the inorganic materials were studied using theoretical model calculations. During the simulations the structure parameters such as materials and thicknesses have been varied. This procedure was repeated several times during the design optimization process including also the feedback from technology and characterization. Two types of VCSEL devices were investigated. The first is an index coupled structure consisting of bottom and top DBR dielectric mirrors. In the space in between them is the cavity, which includes active region and defines the spectral gain profile. In this configuration the maximum electrical field is concentrated in the cavity and can destroy the chemical structure of the active material. The second type of laser is a so called complex coupled VCSEL. In this structure the active material is placed not only in the cavity but also in parts of the DBR structure. The simulations show that such a distribution of the active material reduces the required pumping power for reaching lasing threshold. High efficiency is achieved by substituting the dielectric material with high refractive index for the periods closer to the cavity. The inorganic materials for the DBR mirrors have been deposited by Plasma- Enhanced Chemical Vapor Deposition (PECVD) and Dual Ion Beam Sputtering (DIBS) machines. Extended optimizations of the technological processes have been performed. All the processes are carried out in a clean room Class 1 and Class 10000. The optical properties and the thicknesses of the layers are measured in-situ by spectroscopic ellipsometry and spectroscopic reflectometry. The surface roughness is analyzed by atomic force microscopy (AFM) and images of the devices are taken with scanning electron microscope (SEM). The silicon dioxide (SiO2) and silicon nitride (Si3N4) layers deposited by the PECVD machine show defects of the material structure and have higher absorption in the ultra violet range compared to ion beam deposition (IBD). This results in low reflectivity of the DBR mirrors and also reduces the optical properties of the VCSEL devices. However PECVD has the advantage that the stress in the layers can be tuned and compensated, in contrast to IBD at the moment. A sputtering machine Ionsys 1000 produced by Roth&Rau company, is used for the deposition of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3) and zirconium dioxide (ZrO2). The chamber is equipped with main (sputter) and assisted ion sources. The dielectric materials were optimized by introducing additional oxygen and nitrogen into the chamber. DBR mirrors with different material combinations were deposited. The measured optical properties of the fabricated multilayer structures show an excellent agreement with the results of theoretical model calculations. The layers deposited by puttering show high compressive stress. As an active region a novel organic material with spiro-linked molecules is used. Two different materials have been evaporated by utilizing a dye evaporation machine in the clean room of the department Makromolekulare Chemie und Molekulare Materialien (mmCmm). The Spiro-Octopus-1 organic material has a maximum emission at the wavelength λemission = 395 nm and the Spiro-Pphenal has a maximum emission at the wavelength λemission = 418 nm. Both of them have high refractive index and can be combined with low refractive index materials like silicon dioxide (SiO2). The sputtering method shows excellent optical quality of the deposited materials and high reflection of the multilayer structures. The bottom DBR mirrors for all VCSEL devices were deposited by the DIBS machine, whereas the top DBR mirror deposited either by PECVD or by combination of PECVD and DIBS. The fabricated VCSEL structures were optically pumped by nitrogen laser at wavelength λpumping = 337 nm. The emission was measured by spectrometer. A radiation of the VCSEL structure at wavelength 392 nm and 420 nm is observed.

A pilot investigation of the relationship between climate variability and milk compounds under the bootstrap technique

This study analyzes the linear relationship between climate variables and milk components in Iran by applying bootstrapping to include and assess the uncertainty. The climate parameters, Temperature Humidity Index (THI) and Equivalent Temperature Index (ETI) are computed from the NASA-Modern Era Retrospective-Analysis for Research and Applications (NASA-MERRA) reanalysis (2002–2010). Milk data for fat, protein (measured on fresh matter bases), and milk yield are taken from 936,227 milk records for the same period, using cows fed by natural pasture from April to September. Confidence intervals for the regression model are calculated using the bootstrap technique. This method is applied to the original times series, generating statistically equivalent surrogate samples. As a result, despite the short time data and the related uncertainties, an interesting behavior of the relationships between milk compound and the climate parameters is visible. During spring only, a weak dependency of milk yield and climate variations is obvious, while fat and protein concentrations show reasonable correlations. In summer, milk yield shows a similar level of relationship with ETI, but not with temperature and THI. We suggest this methodology for studies in the field of the impacts of climate change and agriculture, also environment and food with short-term data.

Creación y utilización de actividades multimedia en ciencias.

El problema de partida es la escasa motivación del alumnado frente a las prácticas educativas tradicionales. El grupo se propone el diseño y la realización de actividades motivadoras para la enseñanza de las ciencias. Estas actividades se realizarán en formato multimedia para 1 y 3 de ESO usando el programa CLIC y se complementarán con la elaboración una colección de transparencias. Las actividades multimedia serán de inmediata aplicación con el alumnado del Centro.

Escolarizaci??n y analfabetismo en Asturias : los procesos de alfabetizaci??n popular, 1923-1937

Conocer y analizar la difusi??n de la Instrucci??n Primaria en la sociedad asturiana durante la tercera y cuarta d??cadas de este siglo. Conocer en profundidad el proceso de democratizaci??n cultural en Asturias, hasta qu?? punto y cu??ndo es impulsada, por qu?? fuerzas sociales nuestra regi??n se incorpora al tipo de sociedad alfabetizada y desarrollada culturalmente con la generalizaci??n de la educaci??n. Estudio de las redes escolares y las infraestructuras materiales en la escolarizaci??n regional. Este trabajo est?? dividido en cuatro partes. Previamente se presenta una introducci??n que pretende aproximarnos a la realidad de Asturias desde una perspectiva econ??mica, pol??tica, demogr??fica y social. La primera parte se refiere al analfabetismo. La segunda estudia el proceso de escolarizaci??n partiendo de una introducci??n sobre el estado de la Instrucci??n Primaria en v??speras de la Dictadura primorriverista y aportando un estudio diferenciado para los tres periodos: Dictadura, Transici??n y Rep??blica. La tercera parte se dedica al estudio de las infraestructuras educativas. La parte cuarta se dedica a la instrucci??n post-escolar para mayores de catorce a??os dentro del marco global de la cultura popular. Bibliograf??a. Bibliotecas. Peri??dicos, revistas y publicaciones oficiales. Estudio pormenorizado de la actividad escolar en todos los ayuntamientos asturianos agrupados por ??reas geogr??ficas o partidos judiciales. La situaci??n educativa en 1923 se caracterizaba por una red escolar importante por su volumen, pero deficitaria, inadecuada, asentada en infraestructuras arcaicas, con cifras de asistencia escolar reducidas y con unos deficientes resultados educativos limitados a la adquisici??n de un bagaje cultural m??nimo. La actuaci??n de la Dictadura extendi?? la red escolar p??blica cuando la evoluci??n demogr??fica, la ampliaci??n de la edad escolar y la sociedad m??s lo demandaban. Durante el periodo republicano se crearon m??s escuelas pero, a diferencia del total nacional, en Asturias la mayor??a eran mixtas y unitarias en detrimento de las escuelas graduadas y de p??rvulos. Durante la Guerra Civil se reorganiz?? la Instrucci??n Primaria con la nacionalizaci??n de toda la red escolar a partir de la incautaci??n de las privadas y particulares y se consigui?? un alto nivel de funcionamiento educativo con una cobertura del 83 por ciento de los centros escolares existentes en la zona republicana. En Asturias los procesos de alfabetizaci??n y escolarizaci??n se expanden a lo largo del siglo XX debido a la coincidencia de una doble funcionalidad externa e interna. La externa ven??a dada por el Estado en su objetivo de modernizar el pa??s y la interna, por el deseo de cualificaci??n t??cnica y formaci??n sociopol??tica de los individuos, lo que convirti?? a la alfabetizaci??n y a la instrucci??n en una necesidad.

Estudio de los problemas de convivencia escolar en estudiantes de Educaci??n Secundaria

Elaborar el Cuestionario sobre Problemas de la Convivencia Escolar (CPCE), as?? como analizar su validez (estructura interna) y su fiabilidad (consistencia interna) con el fin de disponer de un instrumento que sea capaz de evaluar los problemas que presenta la poblaci??n adolescente escolarizada, a trav??s de la percepci??n que los docentes mantienen sobre dicha problem??tica. Evaluar la validez externa del CPCE, utilizando como criterio el Cuestionario de Competencia Social, para determinar si el primero de los cuestionarios (CPCE) posee una validez externa aceptable. Analizar la validez y fiabilidad del Cuestionario de Competencia Social. La investigaci??n responde a un dise??o transversal, ya que se estudian distintas variables en el rango de edad que comprende la Educaci??n Secundaria Obligatoria habiendo realizado la recogida de datos sobre esas variables en un mismo momento. Han participado alumnos de dos centros educativos p??blicos (Institutos de Educaci??n Secundaria Obligatoria) de la provincia de Almer??a. Uno de los centros participantes ha sido el Instituto de Educaci??n Secundaria Obligatoria 'La Gangosa-Vistasol', ubicado en el municipio de V??car (Almer??a). El segundo de los centros participantes ha sido el Instituto de Educaci??n Secundaria Obligatoria 'Algazul', ubicado en la localidad de Roquetas de Mar (Almer??a). A trav??s de este cuestionario han sido evaluados un total de 857 sujetos, con un rango de edad entre doce y diecisiete a??os, de los que 437 sujetos son varones (51,0 por ciento de la muestra) y 420 sujetos son mujeres (49,0 por ciento de la muestra), que se hallan cursando estudios de Educaci??n Secundaria Obligatoria. La media de edad es de 14,37, con una desviaci??n t??pica de 1,33. El Cuestionario sobre Problemas de la Convivencia Escolar (CPCE), ha sido construido a partir del an??lisis y categorizaci??n de las conductas-problema descritas en los partes de disciplina emitidas durante el curso acad??mico 2001-02, por 60 profesores y profesoras de los dos Institutos citados. Dadas las caracter??sticas de la investigaci??n, el proceso que se ha llevado a la pr??ctica ha sido bastante laborioso a la vez que largo en el tiempo (tres cursos acad??micos 2000-2001, 2001-2002 y el 2002-2003), ya que ha sido necesario realizar distintas fases en el proceso de investigaci??n. A - La estructura factorial del CPCE es algo diferente de la estructura racional elaborada a priori. Por lo que, en un futuro, habr?? que someterla al an??lisis factorial confirmatorio para ver si la estructura factorial exploratoria se sostiene y simult??neamente es coincidente o no con la estructura racional. Por ello, la primera de las hip??tesis formuladas no se ha llegado a cumplir perfectamente. B - La validez de contenido ha demostrado ser satisfactoria, cumpli??ndose la segunda de las hip??tesis formuladas. C - La validez de criterio ha quedado suficiente y satisfactoriamente probada, por lo que tercera de las hip??tesis formuladas tambi??n se ha cumplido. Se ha comprobado emp??ricamente que a mayor competencia social menos problemas de convivencia escolar manifiestan los alumnos. D - Los distintos factores y dimensiones del CPCE han mostrado tener una adecuada fiabilidad. Esto lleva a ratificar la cuarta de las hip??tesis. E - La escala A del cuestionario SBSS tiene una adecuada adaptaci??n al idioma espa??ol y ha demostrado una adecuada fiabilidad y validez aunque habr?? que reformular o redactar de nuevo algunos ??tems. Esto hace que la quinta y sexta hip??tesis del primer estudio queden cubiertas de forma satisfactoria. F - La edad es una de las variables enormemente discriminativa en relaci??n a los problemas de convivencia escolar, en funci??n de los resultados obtenidos. No sucede lo mismo con el g??nero. Esto hace que la primera hip??tesis del tercer estudio haya quedado cubierta parcialmente. Asimismo, se ha encontrado que otras variables sociodemogr??ficas (la profesi??n de la madre, las relaciones con los hermanos, el centro educativo, el curso escolar, el grupo, las repeticiones en Educaci??n Primaria, las repeticiones en Educaci??n Secundaria) son variables interdependientes en relaci??n a los problemas de convivencia escolar, en funci??n de los aspectos evaluados por el profesorado. G - No se han encontrado, en funci??n de lo comentado en el punto anterior, efectos de interacci??n entre la edad y el g??nero de los adolescentes, por lo que la segunda de las hip??tesis del tercer estudio hay que rechazarla, al menos en esta investigaci??n. En cambio, s?? han aparecido efectos de interacci??n entre la edad y el centro, la edad y el grupo-clase, la edad y las repeticiones en Educaci??n Primaria, la profesi??n de la madre y las relaciones con los hermanos; o la profesi??n de la madre y el grupo-clase.

Bubisher, una nueva biblioteca para el Sahara

Se presenta el proyecto Bublisher y se facilita el enlace a su blog. El proyecto naci?? en el Colegio San Narciso de Mar??n (Pontevedra). Sus alumnos, que ya hab??an colaborado con los refugiados saharauis comprando un cargamento de aud??fonos para los ni??os de los campamentos, tuvieron la idea de hacer llegar a sus escuelas libros de lectura. Cuando 'Escritores por el Sahara' les habl?? de la dificultad de su traslado hasta all??, los alumnos pensaron en un bibliob??s. Aparentemente ingenua, la idea result?? magn??fica, y empez?? a transformarse en realidad, de la mano de la citada asociaci??n de escritores y con el apoyo de numerosas instituciones. Un nuevo proyecto est?? en marcha, la construcci??n de una biblioteca p??blica en Smara.

Actitudes, h??bitos de estudio y rendimiento en Matem??ticas : diferencias por g??nero

Resumen tomado de la publicaci??n

Sensibilidad al dolor, autorregulaci??n, afrontamiento y personalidad en mujeres adultas sanas

Resumen tomado de la publicaci??n