Tesis sobre el tema "Matricide"

Les études épidémiologiques contemporaines attestent d'un taux de morbidité important pour une population à risque relativement jeune, voire tendant à l'augmentation, nous avons souhaité nous pencher sur la problématique anorexique en accordant une attention particulière à l'aménorrhée en tant que troisième terme de la triade symptomatologique ; symptôme à notre sens délaissé à l'instar de l'intérêt psychpathologique suscité par la restriction alimentaire et/ou la hantise de grossir. Aussi, soutenant l'hypothèse de l'existence d'une dimension symbolique afférente à ce symptôme, nous avons tenté d'en rechercher les significations inconscientes. Nous nous sommes aussi intéressée à l'avènement pubertaire et aux menstruations en condensant notre réflexion sous deux angles, soit en se référant d'une part aux travaux psychanalytiques avec des auteurs comme Ph JEAMMET et B. BRUSSET pour ce qui concerne l'anorexie et l'adolescence, ou à H. DEUTSCH ou F. DOLTO pour les menstruations, et d'autre part aux apports psychosomatiques avec J. Mc DOUGALLS ou CH. DEJOURS évoquant les somatisations symbolisantes. Notre étude a porté sur deux suivis menés sur des périodes respectives de six mois et d'un an complétée par l'analyse de deux protocoles projectifs ramassant les données recueillies au test du RORSCHACH et au Thematic Apperception Test. Par l'analyse de ces diverses productions, nous avons essayé de démontrer l'existence d'un fantasme matricide prenant en quelque sorte corps avec la puberté, et témoignant d'une difficulté à intégrer la différence des générations comme à élaborer les pulsions agressives réactivées à l'adresse de l'objet primaire. En cela, avons-nous élaboré la puberté non sous l'angle de la reviviscence du complexe oedipien mais comme une authentique expérience corporelle ayant donné une expression singulière et développant son propre langage, lui-même à décrypter et non pas à interpréter comme écho d'un défaut de l'élaboration mentale
Presents epidemiologies researchs proving for an important morbidity rate with a risking young people with increasing, we wished study for anorexia case with particular mind for amenorrhea in third term of symptomatologic triad, symptom with own opinion forsiken by the way of psychopathologic interest aroused by restricting food on fear to be fat. So, holding the hyptothesus of existence from a symbolic dimension for this symptom, we tried to look for the unconsciousness significances. So we are interested to the puberty advent and menstruations in thinking our mind on two ways, either in using psychanalitics works with authors like PH JEAMMET and B. BRUSSET for anorexia and teenaging or H. DEUTSCH F. DOLTO for menstruations and psychomatics contributions with JM DOUGALLS or CH DELOURS recalling symbolling somatizations. Our research was on two cases, with period for six months and one year, completed by analysis for two projectives protocols from datas with Rorschach test and thematic apperception test. By the analysis from these named productions, we tried to show the existence of a matricid fantasm taking form by some way with puberty, and testifying from difficulty to integrate the difference of generations, like for elaborating aggressives pulsions waked for primary object. So did we talking about puberty and not about teenaging with the oedipe complex way but like a true corporeal experiment with a particular expression, having its proper language, itself to translate and no to integrate like echo for failure of mental elaboration

C’est la rareté du meurtre de la mère par la fille qui nous interroge sur le rôle d’un matricide symbolique féminin. Alors que les meurtres commis par les fils constituent la trame de textes fondateurs, nous avons cherché à comprendre pourquoi la version opposée et féminine n’apparaissait nulle part et si ce n’était pas le signe d’un ratage au cours du développement de la petite fille vers son advenir femme. Pour cela nous avons fouillé différentes mythologies, les trois grandes religions monothéistes, quelques contes populaires, ainsi que des oeuvres littéraires. Il a fallu revisiter le lien mère-fille, puis la relation homme-femme, et enfin terminer sur le rôle du père dans ce ratage. C’est par la préhistoire que nous avons conclu notre travail, en émettant l’hypothèse d’une peur primale chez l’homme, qui l’a poussé à domestiquer la femme. Se trouvant ainsi dévalorisée la femme devenue mère transmet un barrage de la symbolisation qui provoque le ratage du matricide psychique et entraîne sa sempiternelle répétition
It is the rarity of murders committed by daughters on their mothers that leads to questioning on female symbolic matricide. While murders committed by sons are the foundation statements, we went on a quest to find the reason why the opposite feminine version is nowhere visible. Could this be the sign of a failure during the little girl’s developmental process of the girl becoming a woman? For that, we have investigated into various mythologies, the three main monotheist religions, common stories and as well as into some literary works.It has been necessary to re-examine, first the binding mother-daughter relationships, the woman-man relationships and to determine the role of the father in that failure. It is with the Prehistory that we have concluded our work, venturing the hypothesis of a primal fear that pushed the man to domesticate the woman. Feeling underestimated, the woman transmits a symbolisation barrier provoking the failure of the psychic matricide and its eternal recurrence

Thesis (Ph. D.)--University of Oregon, 2001.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 202-212). Also available for download via the World Wide Web; free to University of Oregon users.

La littérature au féminin du XXe siècle est marquée par la récurrence des motifs de la matrophobie et du matricide (Hirsch, 1991 ; Saint-Martin, 1999 ; Giorgio 2002). Dans une perspective comparatiste, la présente étude s’intéresse plus précisément aux années 1945 à 1968, délimitées par six textes de fiction composés par six écrivaines du Québec, de la France et des États-Unis. La notion de sacrifice telle qu’elle a été définie par René Girard (1972 et 1982 notamment) et par Anne Dufourmantelle (2007) est convoquée pour comprendre la représentation textuelle de la matrophobie et du matricide. Combinés à plusieurs analyses féministes de la maternité comme institution (Rich, 1976 ; Irigaray, 1981 ; Olivier, 1980), les définitions et concepts de ces deux théories seront utilisés pour rendre compte des mécanismes horizontaux et verticaux à l’oeuvre dans les textes du corpus. De surcroît, le mythe, dans l’acception que lui a donnée René Girard, sera convoqué comme paradigme, pour saisir les enjeux de la parole sur la mère. À l’issue de la lecture des textes, il apparaît que, dans le corpus, loin d’être synonyme de retour à la paix sociale comme le pose René Girard, le sacrifice des mères et des filles (par identification aux mères) signifie la destruction des sociétés représentées. À ce titre, la présente thèse conclut qu’à une époque riche en bouleversements socioculturels et politiques sur la place et le statut des mères dans les trois pays concernés, ces textes de femmes mettent en image un malaise lié à la maternité instituée ainsi que l’extraordinaire force d’emprise d’une idéologie qui condamne les femmes et les mères à une mort littérale ou symbolique, parfois les deux
Western women’s writing in the twentieth century is marked by the thematic prominence of matricide and matrophobia (Hirsch, 1991; Saint-Martin, 1999 ; Giorgio 2002). Working comparatively, this study addresses the years 1945-1968 as seen through six texts written by women in Quebec, France, and the United States. This study deploys the notion of “sacrifice,” as articulated by René Girard (1972, 1982) and Anne Dufourmantelle (2007), in order to delimit the textual representations of matrophobia and matricide engendered by these works. Drawing on feminist critiques of the “institution” of maternity (Rich, 1976; Irigaray, 1981; Olivier, 1980), this study pursues both a horizontal (systemic and causal) and vertical (learned or inherited) analysis of the act of sacrifice. It further draws on Girard’s seminal exploration of “myth” in order to examine the period’s discursive constructions of the mother. Far from being synonymous with a restoration of social harmony as René Girard argues, the “sacrifice” of mothers (and daughters, through an identification with their mothers) incites the destruction of the societies depicted by these authors. These texts relate women’s unease with the institutions of maternity during a period of political and socio-cultural upheaval regarding the role and status of mothers in the three countries concerned. Through its exploration of the ontology of sacrifice, this thesis illustrates the extraordinary influence of an ideology, which in its time, condemned women and mothers, in some cases, to both a literal and symbolic death

A study was conducted to investigate and identify differences inherent in two subtypes of psychosis driven or mentally disordered homicide: matricide versus any other biological intrafamilial homicide or attempted homicide. Matricide was further investigated through the exploration of offence specific details, as well as demographic and diagnostic characteristics of persons who had committed (or attempted) homicide against the mother and were subsequently found not criminally responsible and detained by the Ontario Review Board between 1992 and 2012. Matricidal accused were more often diagnosed with childhood disorders and paranoid schizophrenia. As adults, they failed to mature sexually and socially, and continued to live at home, dependent on the mothers that were the ultimate victims of their violence. Attachment theory is offered as a proposed explanation for the matricidal impulse.

O presente trabalho tem como objeto de estudo a tragédia Electra de Eurípides no que concerne à atualização que o poeta faz do episódio em sua versão dramática do mito de Orestes. Para tal, divide-se em duas partes, sendo que a primeira compreende o estudo propriamente dito e a segunda traz uma tradução integral do poema dramático seguindo os moldes de uma tradução acadêmica para fins de estudo. O estudo apresenta três capítulos que abordam a questão da atualização sob diferentes perspectivas. O primeiro trata da história do mito desde Homero até sua chegada à poesia dramática e apresenta um estudo comparativo das três versões trágicas que têm o mito por matéria, a saber, a Oresteia de Ésquilo e as Electras de Sófocles e Eurípides. A partir do segundo capítulo, o foco é dado à Electra euripidiana. Parte-se, então, de uma análise pontual de algumas das personagens e do coro com vistas a um estudo dirigido às inovações do enredo. A encenação da tragédia é, por fim, matéria de estudo do terceiro capítulo, ainda sob o ponto de vista da atualização. De uma forma geral, o estudo tem por objetivo uma reflexão sobre os modelos visados por Eurípides, sobre as adaptações que esses sofreram e, finalmente, sobre a recusa de alguns paradigmas.
This thesis focuses on the tragedy Electra by Euripides taking a more specific look at the way the poet updates this episode in his dramatic version of the myth of Orestes. The thesis is divided in two parts. The first contains the study itself and the second offers an integral translation of the dramatic poem according to the standards of academic translations intended for study. The study encompasses three chapters that address the issue of updating from different perspectives. The first concerns the story of the myth from Homer to its appearance in dramatic poetry and presents a comparative study of the three tragic versions of the myth, namely Aeschylus Oresteia and the Electras of Sophocles and Euripides. From the second chapter on, the focus is on Euripides Electra. This chapter resorts to a detailed analysis of some of the characters and the chorus in order to study the innovations in the plot. Finally, the third chapter discusses the staging of the tragedy, once again from the point of view of the updating. Overall, the study intends to reflect on the models used by Euripides, as well as the adaptations that these models have gone through and, finally, the refusal of some paradigms.

Dans la réadaptation d’un mythe, l’évolution des mentalités, notamment en ce qui concerne les représentations familiales, donne lieu à de larges remaniements de l’intrigue proposée par la tradition antique. Le mythe d’Electre, peut-être parce qu’il propose un modèle déjà compliqué à assumer pour les Grecs anciens (un fils tuant sa mère), est l’objet d’une transmission difficile. La rareté des Electre au XVIIe siècle, puis les innovations auxquelles les dramaturges sont contraints pour les adapter dans la seconde moitié du XVIIIe siècle, attestent ces difficultés. Le personnage d’Electre, en tant que sœur, subit des modifications en profondeur, même si elle demeure toujours fidèle à l’idéal de réunion familiale : désormais, cette réunion inclut la mère, ce qui implique un regard très différent sur le matricide. Les réactions de la jeune fille sont parfois difficiles à comprendre ; on peut néanmoins les rattacher, d’un point de vue juridique et social, à des normes auxquelles elles obéissent, même lorsqu’elles semblent les transgresser. La période durant laquelle le mythe d’Electre est le plus dynamique en Europe correspond à un nouvel intérêt pour les relations familiales. L’on peut noter, dans la tragédie, une transition entre des pièces (au XVIIe siècle) où le rôle de la sœur demeure largement indifférencié, vers des pièces (au XIXe) où la sœur est un personnage compris pour la richesse de la relation qu’il entretient avec le frère. Les intrigues consacrées à Electre mettent en avant la relation du frère et de la sœur : cette spécificité contribue à expliquer pourquoi la fable connaît un tel essor, à l’époque même du drame bourgeois
When adapting a myth to theatre, the plot from the original antique tradition is often largely modified to suit the audience’s mentality of the time, especially as far as the reprensentation of the family ties is concerned. Perhaps because it proposes a model which is complicated even for ancient Greeks to accept (that of a son killing his mother)The Electra myth has had a difficult transmission through the ages. The rare occurences of Electra in the XVIIth century, and the necessary innovations that playwriters had to invent to adapt the subject during the second half of the XVIIIth century confirm those difficulties. As a sister, Electra’s character is deeply modified. Even if she remains attached to an ideal of family unity, this reunion now includes the mother, which implies a totally different view of the matricide in the original text. Although the young woman’s reactions are sometimes difficult to understand, from a legal and social point of view they can be linked to the norms to which they obey, even when they seem to break them. The Electra myth is at its most dynamic time in Europe when a new interest in familial relationships is growing. In tragedy, there is a noticible transition between plays in the XVIIth century where the role of the sister is widely unspecialized, to plays in the XIXth century where the sister character is recognised for its rich relationship with the brother. Intrigues dedicated to Electra stress the relationship between the brother and sister: that specificity helps to explain why this antique fable is so popular at the very same time as the drame bourgeois

In questa tesi ci si propone lo studio dell'anello delle matrici quadrate di ordine n, su un campo, per arrivare a dimostrare che ha solo ideali banali pur non essendo un campo. Allo scopo si introducono le operazioni elementari e il procedimento di traduzione di tali operazioni con opportune moltiplicazioni per matrici dette elementari. Si considera inoltre il gruppo generale lineare arrivando a dimostrare che un particolare sottoinsieme delle matrici elementari è un generatore di tale gruppo.

CAPES
Este trabalho aborda a aplicação de uma célula de comutação suave para um conversor matricial. No início do trabalho são apresentadas as características do conversor, apontando suas vantagens e desvantagens. Na sequência, é realizado o estudo da técnica de comutação suave, conhecida como ZVT, que caracteriza-se por não apresentar elementos em série com o circuito matricial. Essa técnica permite que as comutações do conversor matricial ocorram em zero de tensão (ZVS). Para que isso seja possível é utilizado um circuito auxiliar de comutação (CAC). Este circuito tem por finalidade desviar parte do fluxo de potência, permitir a comutação entre as fases do conversor matricial e, na sequência devolver essa energia para a carga. Ainda, esse mesmo circuito realiza as suas comutações, também com condições nulas, isto é, em zero de corrente (ZCS). Todas as etapas necessárias durante as comutações são analisadas; através dos planos de fase, circuitos e das expressões que determinam o tempo de duração de cada etapa. Algumas modificações na atuação do circuito auxiliar são propostas, com a finalidade de reduzir a energia necessária envolvida no processo de comutação. Por fim, para validar o estudo realizado foi implementada uma plataforma de estudos. Nessa plataforma, optou-se pela implementação de um conversor matricial com entrada trifásica e saída monofásica e um circuito auxiliar de comutação. Os resultados obtidos mostram que o circuito auxiliar permitiu que ocorressem as comutações das chaves semicondutoras do circuito matricial em zero de tensão. As modificações propostas possibilitaram que as comutações ocorressem de forma segura, além de garantir a condição nula nos semicondutores, com a redução da quantidade de energia envolvida no processo de comutação.
This paper discusses the application of a switching cell to a soft switching converter matrix. At the beginning of the work are presented the characteristics of the converter, pointing out their advantages and disadvantages. In the sequence, is performed the study on the soft switching technique, known as ZVT, which is characterized by not present the elements in series with the circuit matrix. This technique allows the converter switching matrix occur at zero voltage (ZVS). In order to make this possible is used an auxiliary switching circuit (cac). This circuit has the purpose to divert part of the ow of power, enabling switching between the phases of the matrix converter and, following return this energy to the load. Also, this same circuit performs its switching also with null conditions, i.e. at zero current (ZCS). All steps required during the commutations are analyzed; through phase circuits plans and expressions that determine the duration of each stage. Some changes in the performance of the auxiliary circuit are proposed in order to reduce the energy required in the process of switching. Finally, to validate the study was implemented a platform for studies. On this platform, we chose to implement a converter matrix with three-phase input and single phase output and a switching auxiliary circuit. The results show that the auxiliary circuit allowed to occur semiconductor switches of the switching matrix circuit at zero voltage. The proposed modifications have enabled the commutations occur in safe form, besides ensuring null condition in the semiconductor by reducing the amount of energy involved in the switching process.

The introduction of parallel processing architectures allows the reduction of computation time by mapping the algorithm over a network of cooperating processors. However, to take advantage of the processing power of these architectures, the programmer, due to the lack of appropriate tools, must spend a considerable amount of time in the parallelization of the algorithm. Another problem with the conventional parallel programming model is that the parallelization of these algorithms is strongly dependent on the hardware used, so portability and upgradability are also time consuming steps in the development process. This way, the development time of efficient parallel applications, with the conventional tools available, is many times superior to the development time of a sequential application. As a response to the above constrains suggested, the programming environment which is proposed in this thesis, can automatic generate a parallel version of a matrix algorithm, from a sequential description. This environment can be decomposed in successive levels of abstraction, from the hardware, and the parallel processing model, rising to the top level, where a virtual sequential processing model is presented. At this level, from a sequential description of the algorithm, and a block diagram of the processor network, the parallel algorithm is automatically generated. This abstraction level implementation was designed to allow an higher level of portability and flexibility, so that the extension of the proposed environment to handle new processors, with different specifications in terms of computation and communication, can be easily accomplished. The environment also allows an easy expansion of the basic linear algebra library included, to meet new algorithms demand. To show the proposed environment, and the performance of the automatically generated parallel algorithms, two cases of implementation are studied.
A introdução de arquitecturas de processamento paralelo permitiu que o tempo de processamento de um algoritmo possa ser reduzido dividindo o esforço computacional por mais do que um processador. Todavia para se tirar partido destas arquitecturas, devido à falta de ferramentas apropriadas, o projectista despende uma considerável quantidade de tempo na paralelização do algoritmo sequencial. Outro problema normalmente encontrado, no modelo de programação paralelo, relaciona-se com o facto de a paralelização destes algoritmos ser altamente dependente da arquitectura objecto. Assim, a portabilidade e adaptabilidade destas aplicações são tarefas consumidoras de tempo de desenvolvimento. Pelas razões apontadas, o tempo de implementação de um algoritmo paralelo é muito superior ao tempo de implementação sequencial do mesmo algoritmo. Tais condições constituíram a motivação para o trabalho desenvolvido nesta tese, o qual consiste num sistema de paralelização automático de algoritmos matriciais. Este sistema é visto como um conjunto de níveis de abstracção que gradualmente se afastam do modelo de processamento paralelo e se aproximam do modelo sequencial. No nível mais elevado basta uma descrição do algoritmo, numa linguagem sequencial, e um diagrama de blocos da rede de processadores, para que o sistema, automaticamente, gere o código paralelo para a rede objecto. Esta implementação, baseada em sucessivos níveis de abstracção, permite um elevado grau de portabilidade e flexibilidade do sistema, de modo que a introdução de novos processadores, com diferentes especificações de computação e comunicação, ou de operações matriciais não incluídas na biblioteca matricial que acompanha o sistema, seja uma tarefa facilitada. Finalmente é estudada a paralelização automática de dois algoritmos, de modo a demonstrar o modelo de programação proposto bem como o desempenho dos algoritmos paralelos automaticamente gerados.

Orientador: Sueli Irene Rodrigues Costa
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica
Made available in DSpace on 2018-08-20T11:38:10Z (GMT). No. of bitstreams: 1 Ferrari_AgnaldoJose_D.pdf: 2344410 bytes, checksum: faa96ccdd8ff4ec461abc4f69d6cc999 (MD5) Previous issue date: 2012
Resumo: Neste trabalho abordamos a construção de reticulados usando propriedades da Teoria Algébrica dos Números. Enfocamos a construção de alguns reticulados com características especiais, conhecidos na literatura, via reticulados ideais, através de uma abordagem matricial e algorítmica...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital
Abstract: In this work we approach lattice constructions using properties of algebraic number theory. One focus is on the construction of some well known lattices via ideal lattices, through a matrix and algorithmic approach...Note: The complete abstract is available with the full electronic document
Doutorado
Matematica Aplicada
Doutor em Matemática Aplicada

Neste trabalho, apresentamos o problema contextualizado como alternativa pedagógica para o ensino e a aprendizagem da Matemática no Ensino Médio, bem como algumas atividades relacionadas ao conceito de matrizes. Realizamos, inicialmente, algumas considerações sobre a Criptografia, que é o contexto gerador das atividades contextualizadas. Em seguida, procuramos discutir a importância do ensino de matrizes no Ensino Médio segundo documentos oficiais – os Parâmetros Curriculares Nacionais do Ensino Médio e as Diretrizes Curriculares da Educação Básica da Secretaria de Estado da Educação do Paraná. Por fim, a partir da releitura do drama shakespeariano – Romeu e Julieta, desenvolvemos o estudo de matrizes e suas operações, apresentando cinco problemas contextualizados com a Criptografia.
In this paper, we present the context of alternative pedagogical issues for teaching and learning of Mathematics in high school, as well as some activities related to the concept of matrix. We conducted initially some considerations about the encryption, which is the generative context of the contextualized activities. Next, we seek to discuss the importance of teaching about matrices in high school according to official documents – National Curriculum of High School and Basic Education Curriculum Guidelines of the Ministry of Education of Paraná. Finally, from the retelling of the Shakespearian drama – Romeo and Juliet –, we developed the study of matrices and their operations, featuring five contextualized problems with Encryption.

Orientador: Alagacone Sri Ranga
Banca: Cleonice Fátima Bracciali
Banca: Jorge Manuel Vieira Capela
Resumo: Neste trabalho estudamos uma construção dos polinômios ortogonais usando uma abordagem matricial. Para isto, consideramos algumas propriedades de uma determinada classe de matrizes infinitas que possuem papel importante na determinação e representação de certas sequências polinomiais. Tais propriedades permitem a obtenção de alguns resultados clássicos da teoria de polinômios ortogonais. Usando a mesma abordagem, discutimos algumas caracterizações dos polinômios ortogonais clássicos
Abstract: In this work we study a construction of orthogonal polynomials using a matrix approach. For this purpose, we consider properties of a certain class of infinite matrices that play an important role in determination and representation of some polynomial sequences. These properties are useful to obtain some classical results in the theory of orthogonal polynomials. Using the same approach, we discuss some characterizations of classical orthogonal polynomials
Mestre

Beaucoup de résultats sur l’estimation d’une matrice d’échelle en analyse multidimensionnelle sont obtenus sous l’hypothèse de normalité (condition sous laquelle il s’agit de la matrice de covariance). Or il s’avère que, dans des domaines tels que la gestion de portefeuille en finance, cette hypothèse n’est pas très appropriée. Dans ce cas, la famille des distributions à symétrie elliptique, qui contient la distribution gaussienne, est une alternative intéressante. Nous considérons dans cette thèse le problème d’estimation de la matrice d’échelle Σ du modèle additif Yp_m = M + E, d’un point de vue de la théorie de la décision. Ici, p représente le nombre de variables, m le nombre d’observations, M une matrice de paramètres inconnus de rang q < p et E un bruit aléatoire de distribution à symétrie elliptique, avec une matrice de covariance proportionnelle à Im x Σ. Ce problème d’estimation est abordé sous la représentation canonique de ce modèle où la matrice d’observation Y est décomposée en deux matrices, à savoir, Zq x p qui résume l’information contenue dans M et une matrice Un x p, où n = m - q, qui résume l’information suffisante pour l’estimation de Σ. Comme les estimateurs naturels de la forme Σa = a S (où S = UT U et a est une constante positive) ne sont pas de bons estimateurs lorsque le nombre de variables p et le rapport p=n sont grands, nous proposons des estimateurs alternatifs de la forme ^Σa;G = a(S + S S+G(Z; S)) où S+ est l’inverse de Moore-Penrose de S (qui coïncide avec l’inverse S-1 lorsque S est inversible). Nous fournissons des conditions sur la matrice de correction SS+G(Z; S) telles que ^Σa;G améliore^Σa sous le coût quadratique L(Σ; ^Σ) = tr(^ΣΣ‾1 - Ip)² et sous une modification de ce dernier, à savoir le coût basé sur les données LS (Σ; ^Σ) = tr(S+Σ(^ΣΣ‾1 - Ip)²). Nous adoptons une approche unifiée des deux cas où S est inversible et S est non inversible. À cette fin, une nouvelle identité de type Stein-Haff et un nouveau calcul sur la décomposition en valeurs propres de S sont développés. Notre théorie est illustrée par une grande classe d’estimateurs orthogonalement invariants et par un ensemble de simulations
Numerous results on the estimation of a scale matrix in multivariate analysis are obtained under Gaussian assumption (condition under which it is the covariance matrix). However in such areas as Portfolio management in finance, this assumption is not well adapted. Thus, the family of elliptical symmetric distribution, which contains the Gaussian distribution, is an interesting alternative. In this thesis, we consider the problem of estimating the scale matrix _ of the additif model Yp_m = M + E, under theoretical decision point of view. Here, p is the number of variables, m is the number of observations, M is a matrix of unknown parameters with rank q < p and E is a random noise, whose distribution is elliptically symmetric with covariance matrix proportional to Im x Σ. It is more convenient to deal with the canonical forme of this model where Y is decomposed in two matrices, namely, Zq_p which summarizes the information contained in M, and Un_p, where n = m - q which summarizes the information sufficient to estimate Σ. As the natural estimators of the form ^Σ a = a S (where S = UT U and a is a positive constant) perform poorly when the dimension of variables p and the ratio p=n are large, we propose estimators of the form ^Σa;G = a(S + S S+G(Z; S)) where S+ is the Moore-Penrose inverse of S (which coincides with S-1 when S is invertible). We provide conditions on the correction matrix SS+G(Z; S) such that ^Σa;G improves over ^Σa under the quadratic loss L(Σ; ^Σ) = tr(^ΣΣ‾1 - Ip)² and under the data based loss LS (Σ; ^Σ) = tr(S+Σ(^ΣΣ‾1 - Ip)²).. We adopt a unified approach of the two cases where S is invertible and S is non-invertible. To this end, a new Stein-Haff type identity and calculus on eigenstructure for S are developed. Our theory is illustrated with the large class of orthogonally invariant estimators and with simulations

Buscamos apreender, a partir de uma abordagem etnometodológica, as representações sociais sobre violência e criminalidade construídas em torno do julgamento do Caso Richthofen . A questão da Lei, ou melhor, da quebra da Lei representada no ato de Suzane Richthofen, ao planejar e matar os seus pais revela, sobretudo, um esgarçamento dos laços de constituição do pacto social em torno do Poder (Social/Paterno/Materno) na contemporaneidade. Através da mídia digital, acompanhamos as construções discursivas produzidas pelos internautas que se posicionaram sobre o crime em questão, durante o processo de julgamento do mesmo. Deste modo, analisamos a mídia digital como um lugar privilegiado de produção e expressão de representações sociais através das quais procuramos apreender as relações sociais que constituem um novo tipo de poder o poder da tecnologia da informação nos rumos da sociabilidade contemporânea. O sujeito, a família (em seus papéis sociais) e os diversos atores sociais envolvidos no julgamento do Caso Richthofen , contextualizados na extrema barbárie e no horror do ato parricida, remete-nos à percepção social de uma crise institucional expressa tanto pela insuficiência da Constituição para regular as relações no campo social, como pela falha na vivência de emoções e sentimentos positivos que contribuir para a produção de uma coesão social imprescindíveis para ordenar os sujeitos no campo social.

Pour mieux comprendre le developpement et la progression des adenomes hypophysaires humains, nous avons compare la structure et la composition du stroma adenomateux a celles du tissu conjonctif de l'antehypophyse humaine normale, ainsi que l'expression des recepteurs de la matrice extra-cellulaire au niveau des cellules normales et adenomateuses. Nos principaux resultats sont les suivants: (1) la formation et la progression des adenomes hypophysaires sont associees au developpement d'un stroma qui presente des alterations structurales remarquables par rapport au tissu conjonctif et a la vascularisation de la glande normale ; (2) les adenomes hypophysaires progressent a l'interieur du parenchyme normal par un processus actif qui impliquerait la desorganisation et la destruction du tissu conjonctif normal et la colonisation progressive des cordons juxta-tumoraux de cellules normales par les cellules adenomateuses ; (3) les changements phenotypiques de la vascularisation adenomateuse, par rapport au tissu normal, sont accompagnes d'une expression differentielle des isoformes de la laminine et de la fibronectine dans les vaisseaux tumoraux ; (4) en comparaison avec l'antehypophyse normale, les adenomes presentent des alterations profondes de l'expression des recepteurs aux composants de la matrice extra-cellulaire appartenant a la famille des integrines, aussi bien dans les cellules tumorales que dans les cellules du stroma

La mise au point d'un appareillage performant de double résonnance pour étudier la relaxation vibrationnelle en matrice nous a permis d'obtenir un grand nombre de résultats expérimentaux dans une gamme de temps s'étendant de la nanoseconde à la milliseconde. Dans le cas de SF₆, nos mesures mettent en évidence une série de transferts intramoléculaires suivie de la relaxation du niveau le plus bas par transfert direct d'énergie aux modes de translation. Pour NH₃, une relaxation assistée par l'inversion ou par la rotation est invoquée pour expliquer les résultats dans les matrices de gaz rares et l'anomalie observée avec la matrice d'azote. D'un point de vue plus général, nous discutons les deux approches qui ont été utilisées pour décrire la relaxation : multiphonon ou collisions binaires Isolées et nous montrons qu'une voie intermédiaire peut être trouvée à partir d'une analogie avec la dissociation des complexes de Van der Waals
An efficient double resonance apparatus has allowed us to study the vibrational relaxation of matric isolated molecules with a time resolution as short as a few nanoseconds. In the SF₆ case, a cascade of fast intramolecular transfers is followed by the decay of the lowest level directly to the translational modes. For NH₃, a rotation of inversion assisted process is invoqued to explain the rare gas matrices results and the anomaly observed in nitrogen matrix. On a theoretical point of view, we discuss the two classes of models that have been used to describe the relaxation: multiphonon and isolated binary collisions and we show that an intermediate possibility may be given by an analogy with the vibrational dissociation of Van der Waals complexes

Les proprietes d'un materiau composite dependent non seulement des proprietes intrinseques des elements constituants, la fibre et la matrice, mais egalement de l'interface les separant. Une bonne liaison interfaciale est essentielle a un transfert de contrainte efficace entre la matrice et la fibre. Deux approches differentes d'amelioration de l'adhesion fibre/matrice ont ete etudiees: enrobage de fibres avec un ensimage specifique a la matrice et utilisation d'une technique de fabrication reactive in-situ pour greffer des groupements fonctionnels au squelette du polymere afin d'activer la matrice. Les deux systemes, modification par ensimage et modification de la matrice, ont ete examines dans les materiaux composites renforces par les fibres de verre-e, respectivement, a matrice polyamide 6. 6 et polypropylene. Les constituants, la fibre, l'ensimage et la matrice ont ete analyses individuellement, puis combines dans le materiau composite. Trois methodes d'evaluation de la resistance de la liaison fibre/matrice ont ete developpees: le modele d'efficacite d'adhesion, l'analyse viscoelastique et le test de la microgoutte

La fattorizzazione matriciale non negativa (NMF) è un metodo di riduzione di dimensione lineare recentemente studiato nell'ambito dell'analisi dei dati per le sue proprietà di estrazione di informazioni facilmente interpretabili da una matrice dei dati non negativa. Dopo una breve rassegna sulle approssimazioni matriciali a rango ridotto passiamo allo studio di alcuni algoritmi standard per la risoluzione della NMF. Sfruttiamo poi gli stessi per effettuare esperimenti in due ambiti applicativi: il text mining e il riconoscimento facciale. Infine introduciamo una variante ortogonale del problema, chiamata ONMF, di cui riportiamo l'equivalenza matematica con una variante pesata del metodo delle k-medie sferiche. Questo risultato consente di svolgere un confronto tra i risultati ottenuti da diversi algoritmi nel clustering di immagini iperspettrali.

Šio darbo metu nustatyta, kad fotosensibilizacija efektyvus metodas Gram teigiamų maisto patogenų inaktyvacijai in vitro, nuo pakuočių bei maisto matricų paviršiaus. Rezultatai in vitro rodo, kad pasiekiama pilna patogeninių mikroorganizmų inaktyvacija (7 log). Modelinėje sistemoje atlikus patogenų adheziją ant poliolefino paviršiaus gauta visiška jų inaktyvacija fotosensibilizacijos būdu. Dėl nereguliarių paviršių patogenų inaktyvavimas ant maisto matricų yra sudėtingesnis ir mažiau efektyvus nei in vitro, tačiau pasiekta 2-3 log inaktyvacija rodo, kad fotosensibilizacija gali būti naujas metodas maisto produktų mikrobiologiniam saugumui užtikrinti.
This work revealed that photosensitization could be effective method for decontamination of Gram positive foodborne pathogens in vitro, from packaging material and different food matrix. Obtained results in vitro suggest that full inactivation of pathogenic microorganisms (7 log) can be achieved. After adhesion of pathogens onto polyolefine surface full inactivation by photosensitization was achieved. Due to different and complicated surfaces the efficacy of photosensitization on food matrix was a little bit lower. However, food pathogens inactivation by 2-3 log is enough for photosensitization to be one of the newest techniques for microbiological food control.

Ce travail est consacré aux approximants de Padé. On commence par une amélioration du calcul des coefficients des polynômes orthogonaux par rapport à une fonctionnelle linéaire quelconque en utilisant la méthode Cestac de J. Vignes. On étend les notions d'approximants de Padé en deux points des séries formelles aux séries de fonctions. On étend également la méthode de C. Brezinski, pour l'estimation de l'erreur des approximants de Padé en un point dans le cas normal, au cas non normal et au cas des approximants de Padé en deux points. On étudie la stabilité et la convergence des formules de quadrature de Gauss pour une fonction poids polynomiale de degré inferieur ou égal à 2. Enfin, les approximants de Padé matriciels rectangulaires ayant des polynômes générateurs à coefficients matriciels carrés sont définis ; des relations de récurrence que vérifient ces polynômes sont établies. On obtient un algorithme QD matriciel ; on généralise le théorème de Shohat-Favard et on étend la procédure de Kronrod pour l'estimation de l'erreur de ces approximants.

Le funzioni di matrici giocano un ruolo importante in molte applicazioni. Tra le funzioni di matrici più studiate in analisi numerica vi è l'esponenziale di matrice che è fondamentale nell'ambito delle equazioni differenziali lineari. Vista l'importanza ricoperta dall'esponenziale di matrice, in questo testo verranno mostrate alcune sue proprietà, seguite da un importante metodo di calcolo e da altri algoritmi per il calcolo dell'esponenziale di matrice, mostrando con un esempio numerico le differenze tra i diversi metodi.

Questo elaborato ha lo scopo di presentare un algoritmo di clustering gerarchico per matrici iperspettrali ad alta risoluzione. Dato un set di immagini che contiene copie della stessa fotografia scattate a diverse lunghezza d'onda luminose, l'obiettivo è quello di determinare gli elementi che appaiono nell'immagine. Gli algoritmi che permettono di separare gli elementi costitutivi di un'immagine sono detti algoritmi di blind hyperspectral unmixing e trovano applicazioni in svariati campi tra cui l'analisi delle immagini. In particolare, sono utilizzati in medicina per esaminare le culture batteriche e in radiologia per la diagnostica di immagini, in chimica per analizzare il risultato di alcune reazioni e per monitorare l'inquinamento, ma anche nell'industria alimentare per controllare la qualità del cibo. Per esempio, uno dei dataset di immagini iperspettrali più diffusi è quello di Cuprite che raffigura una zona mineraria situata nel sud del Nevada. L'algoritmo applicato a questo set ha rivelato la presenza di più di 15 minerali differenti tra cui alunite, montmorillonite, goethite, ossidi di ferro e molti altri. Inizialmente sarà presente un unico cluster contenente tutti i pixel. A ogni iterazione si selezionerà il cluster in modo da minimizzare l'errore al passo successivo e si separerà il cluster scelto in due. In seguito si utilizzerà una fattorizzazione matriciale di rango due (NMF) al fine di spezzare il cluster. Si illustrerà poi come questo metodo possa essere applicato a differenti matrici iperspettrali come algoritmo di estrapolazione degli elementi presenti nei dataset. Infine, si confronterà il metodo proposto e l'algoritmo classico delle k-medie e si discuteranno le prestazioni dei due metodi su matrici iperspettrali reali.

Il lavoro della presente tesi è stato svolto nell'ambito di un progetto avente come scopo principale lo sviluppo di una nuova tecnica di imaging per la ricostruzione di tracce di particelle in un rivelatore ad argon liquido. Si vuole sfruttare la luce di scintillazione emessa dall'argon per realizzare immagini di tali tracce. A questo fine, è necessario utilizzare un dispositivo di imaging, composto da un sistema ottico e da un sensore. Per quanto riguarda il sistema ottico, si è optato per una maschera ad apertura codificata, mentre come sensori si intende utilizzare matrici di silicon photomultiplier (SiPM) con un elevato numero di canali. In particolare, il lavoro di questa tesi si è focalizzato sulla caratterizzazione delle matrici di SiPM impiegate. Grazie a tale sistema, sono state effettuate le prime misure che hanno indicato la fattibilità di questa tecnica innovativa per la ricostruzione di immagini.

L'idee d'utiliser les proprietes avantageuses de la lumiere pour realiser un processeur optique est apparue vers la fin des annees 60. Depuis, de nombreuses architectures dediees au calcul de produits matriciels ont ete proposees. La caracteristique principale de ces systemes est d'operer un codage transversal des elements des matrices traitees, ce qui, par nature, en fait des architectures 2d. Les recherches menees au laboratoire d'optique de besancon depuis une dizaine d'annees sur des architectures systoliques de processeurs optiques ont permis d'utiliser une autre forme de codage de l'information : la technique de modulation de coherence (mdc). Nous montrons dans ce manuscrit, qu'il est possible de coupler les avantages d'un codage transversal bidimensionnel avec ceux apportes par l'utilisation de la mdc (codage longitudinal). L'architecture ainsi developpee permet de definir un processeur 3d, c'est-a-dire volumique. Le premier chapitre de ce memoire sera consacre a une etude des montages optiques realises ces 25 dernieres annees pour calculer des produits matriciels. Le deuxieme chapitre permettra d'introduire le principe de la modulation de coherence. Nous decrirons alors les architectures systoliques particulieres, developpees au laboratoire d'optique de besancon, qui s'appuient sur cette methode. Le processeur realise sera detaille au chapitre iii. Nous soulignerons les proprietes specifiques liees a l'utilisation de modulateurs a cristaux liquides nematiques twistes. Nous souleverons alors certains problemes de codage des donnees numeriques, et examinerons les solutions que nous avons adoptees. Nous presenterons au chapitre iv les resultats experimentaux. Le chapitre v permettra d'exposer les ameliorations et les differentes perspectives qu'il serait possible d'apporter a notre architecture. Enfin, nous presenterons au chapitre vi, une application etonnante de la modulation de coherence au codage secret d'informations.

Cette these presente des algorithmes de programmation lineaire et de calcul matriciel. Le premier chapitre est consacre a la programmation lineaire. L'introduction de variables d'ecart quadratiques transforme le probleme initial en un probleme non lineaire, resolu de facon iterative a l'aide de deux algorithmes de type newton. Leur convergence est lineaire pour le premier, quadratique pour le second. La comparaison avec des resultats numeriques obtenus par la methode de karmarkar montre l'interet de notre methode. Une methode de resolution de systemes lineaires reguliers est presentee dans le deuxieme chapitre ; la comparaison avec la methode de gauss montre que les deux methodes sont analogues, la notre presentant l'interet d'offrir un degre de parallelisation superieur. Les deux derniers chapitres rassemblent deux articles traitant du calcul de l'inverse d'une matrice hessenberg et de l'ordre de multiplicite de valeurs propres reelles d'une matrice tridiagonale

Doutoramento em Matemática
Nesta dissertação é apresentada uma abordagem a polinómios de Appell multidimensionais dando-se especial relevância à estrutura da sua função geradora. Esta estrutura, conjugada com uma escolha adequada de ordenação dos monómios que figuram nos polinómios, confere um carácter unificador à abordagem e possibilita uma representação matricial de polinómios de Appell por meio de matrizes particionadas em blocos. Tais matrizes são construídas a partir de uma matriz de estrutura simples, designada matriz de criação, subdiagonal e cujas entradas não nulas são os sucessivos números naturais. A exponencial desta matriz é a conhecida matriz de Pascal, triangular inferior, onde figuram os números binomiais que fazem parte integrante dos coeficientes dos polinómios de Appell. Finalmente, aplica-se a abordagem apresentada a polinómios de Appell definidos no contexto da Análise de Clifford.
In this thesis an approach to multidimensional Appell polynomials is presented with special relevance for the structure of their generating function. This structure, together with an adequate choice of an ordering for the monomials that are present in the polynomials, gives a unifying nature to our approach and allows the representation of Appell polynomials by means of block matrices. Such matrices are constructed from another matrix with simple structure, called creation matrix, which is a sub-diagonal matrices whose nonzero entries are the successive natural numbers. The exponential of this matrix is the well known lower triangular Pascal matrix, lower triangular, where the binomial numbers appear as part of the coefficients of Appell polynomials. Finally, the presented approach is applied to Appell polynomials defined in the context of Clifford Analysis.

Les héparane sulfate protéoglycanes (HSPG) sont, comme l’ensemble des protéoglycanes (PG), constitués d’une partie protéique et d’un glycosaminoglycane (GAG), en l’occurrence l’héparane sulfate (HS) pour les HSPG. Ils font partie intégrante de la matrice extracellulaire (MEC). Les PG sont capables, par leurs GAG, de lier un certain nombre de partenaires tels que les facteurs de croissance, chemokines, cytokines ou enzymes. Ils régissent donc la biodisponibilité de nombreux médiateurs solubles et par conséquent leur activité biologique. Ils sont ainsi impliqués dans la régulation de nombreux processus tels que la prolifération, la différenciation, le remodelage tissulaire, l’angiogenèse... De plus, il a été démontré que la liaison de protéines possédant un site heparan binding (HB) avec l’HS des HSPG les protégent de la dégradation enzymatique. Cependant, les HSPG sont parmi les premiers composants de la MEC à être digérés par les héparanases cellulaires lors d’agressions tissulaires. Cette digestion rend les sites HB disponibles et les protéines sensibles à la dégradation protéolytique. C’est donc dans le but de protéger les HSBP (heparan sulfate binding protein) qu’a été développée la technologie des héparanes mimétiques (HM) qui vont se substituer aux HS dégradés sur les sites HB disponibles et protéger les protéines du milieu lésé. Ces HM, déjà utilisés comme agent thérapeutique de la MEC, sont désignés, dans cette utilisation, sous le sigle RGTA pour regenerating agent puisqu’ils augmentent la vitesse et la qualité de la réparation tissulaire, pouvant conduire à une véritable régénération des tissus. Lors du développement tumoral et métastatique, il a été démontré que l’activité enzymatique des héparanases est démultipliée, responsable d’une dégradation accrue des HS. Dans ce contexte, les HM vont pouvoir se fixer sur cette matrice lésée d’où l’idée de leur utilisation diagnostique en cancérologie. L’utilisation d’HM marqué (HM*) par un radioisotope tel que le fluor 18 (18F) et suivi par imagerie moléculaire TEP-Scan (tomographie par émission de positons associée au scanner) devrait permettre un marquage particulièrement efficace des matrices environnant les cellules tumorales et métastasées. Les HM* pourraient, en effet, cibler la MEC impliquée, par sa dégradation précoce, dans les processus de croissance et de dissémination tumorale et devenir un nouveau marqueur oncologique en imagerie moléculaire. A ce jour, parmi les différents marqueurs oncologiques étudiés, aucun ne s’adresse au compartiment matriciel. L’usage des HM* devrait ainsi permettre la détection des zones péri-tumorales et trouver une place dans le diagnostic précoce du cancer et son suivi thérapeutique
Heparan sulfate proteoglycans (HSPG), like all proteoglycans (PG), consisting of a protein portion and a glycosaminoglycan (GAG), heparan sulphate (HS) for HSPG. They are part of the extracellular matrix (ECM). PG are able, through their GAG, to bind a number of partners such as growth factors, chemokines, cytokines or enzymes. They regulate the bioavailability of many soluble mediators and thus their biological activity. They are thus involved in the regulation of many processes such as proliferation, differentiation, tissue remodeling, angiogenesis... In addition, it was shown that the binding of proteins having a heparan binding site (HB) with HS of HSPG protect them from enzymatic degradation. However, HSPG are among the first components of the ECM to be digested by heparanase during cellular tissue damage. This digestion makes HB sites available and proteins are sensitive to proteolytic degradation. It is in order to protect the HSBP (heparan sulfate binding protein) that was developed technology heparan mimetics (HM) that will replace the degraded HS on available HB sites and protect proteins of middle injured. These HM, already used as a therapeutic agent of the ECM, are identified in this use under the symbol RGTA for regenerating agent because they increase the speed and quality of the tissue repair, potentially leading to a true tissue regeneration. During tumor development and metastasis, it has been shown that the enzymatic activity of heparanase is multiplied, leading to an increased degradation of HS. In this context, the HM will be able to fix this matrix injured hence the idea of their diagnostic use in oncology. Using labeled HM (HM*) with a radioisotope such as fluorine-18 (18F) and followed by molecular imaging PETScan (positon emission tomography with scanner associated) should allow a particularly efficient marking of the matrix surrounding metastatic and tumor cells. HM* could indeed target ECM involved, through its early degradation in the processes of tumor growth and tumor spread and become a new marker oncology in molecular imaging. To date, among the various studied cancer markers, none address the matrix compartment. The use of HM* should allow the detection of peri-tumor and find a place in the early diagnosis of cancer and the therapeutic monitoring

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Infiltração é o processo pelo qual a água passa da superfície para o interior do solo, sendo dependente da carga hidráulica na superfície, do teor de água inicial, da textura, da estrutura, da condutividade hidráulica e da porosidade do solo. Diversos modelos se propõem a estimar este processo, dentre os quais se destaca o de Green-Ampt modificado por Mein e Larson (GAML), baseado numa análise física do processo. Embora seja bastante utilizado, este modelo apresenta como desvantagem a dificuldade de obtenção de seus parâmetros de entrada, principalmente do potencial matricial na frente de umedecimento ( ψ m ). Assim sendo, este trabalho teve como objetivos: obter as variáveis necessárias à estimativa do potencial matricial na frente de umedecimento, utilizando-se para tal o modelo de Green-Ampt modificado por Mein e Larson, e estabelecer modelo matemático que relacione o potencial matricial na frente de umedecimento com as características físicas e a condutividade hidráulica do solo saturado, para sua aplicação no modelo de Green-Ampt modificado por Mein e Larson. Foram utilizadas três classes de solos (Latossolo Vermelho - Amarelo – LVA; Latossolo Vermelho – LV; e Argissolo Vermelho – PV). Estes solos foram secos ao ar, destorroados e peneirados em peneira de malha 10 mm, sendo posteriormente acondicionados em colunas de PVC de 200 mm de diâmetro e 800 mm de altura, de modo que a densidade do solo ficasse próxima daquela observada em campo. Na lateral das colunas, foram instaladas horizontalmente sondas de TDR para a determinação do teor de água e para o acompanhamento da frente de umedecimento. Aplicou-se água sobre a superfície das colunas sob taxa constante, por meio de um simulador de chuvas, sendo que o excesso escoado superficialmente foi conduzido para uma caixa de coleta na qual foi instalado um medidor de nível denominado Thalimedes. O volume infiltrado foi determinado por diferença entre o volume precipitado e o escoado. Após a realização dos testes, foram coletadas amostras de solo para determinação da granulometria, densidade do solo, porosidade, macroporosidade e microporosidade. Foram determinados, ainda, os teores volumétricos de água na zona de transmissão e no início do processo e a condutividade hidráulica do solo saturado. O potencial matricial foi calculado por intermédio de um rearranjo no modelo de GAML, considerando a taxa de infiltração estável (Tie) como representativa da condutividade hidráulica do solo saturado e o teor volumétrico de água na zona de transmissão em lugar do teor volumétrico de água correspondente à saturação. De posse dos valores de ψ m e das características do solo, foram ajustados modelos de regressão, sendo a escolha do melhor modelo feita por meio dos coeficientes de determinação (R 2 ), pela significância dos parâmetros no modelo, pelo menor número de variáveis envolvidas e pela facilidade de obtenção dessas variáveis (características do solo). Os valores de condutividade hidráulica do solo saturado, de porcentagem de silte e de macroporosidade foram significativos em todos os modelos nos quais foram utilizados. A Tie não foi significativa em nenhum dos modelos. Todas as equações obtidas utilizando-se a porcentagem de silte em combinação com outras variáveis apresentaram bons resultados na modelagem do ψ m , sendo que, os melhores resultados foram obtidos para o modelo que relaciona o ψ m com a porosidade, a condutividade hidráulica do solo saturado e a porcentagem de silte.
Infiltration is the process by which water passes through the soil surface down to the soil, being dependent on hydraulic load in the surface, on the antecedent moisture, on texture, structure, soil hydraulic conductivity and soil porosity. Several models aim to estimate this process, among which the Green-Ampt modified by Mein and Larson (GAML) model is based on a physical analysis of the process. Although it is frequently used, this model has a limitation for obtaining input parameters, such as the potential head at the wetting front ( ψ m ). This work aimed to obtain the ψ m for GAML model for soils typical of tropical areas, using three classes of soils (Red-Yellow Oxisol, Red Ultisol and Red Oxisol). These soils were air-dried, ground and sieved through 10 mm mesh sieve, placed in PVC columns of 200 mm diameter and 800 mm height, so that the soil density was similar to the field. In the lateral of the columns, horizontal TDR probes were installed for the moisture determination and for the monitoring of the wetting front. The water was applied to the surface of the columns at a constant rate by means of a rain simulator device and the excess drained superficially, was collected and measured in a box using a “Thalimedes” device. The infiltrated volume was calculated by the difference among the precipitate volume and the runoff. After the tests, soil samples were collected for determination of the texture, soil density, porosity, macroporosity, microporosity, volumetric moisture (before and after the tests) and soil hydraulic conductivity. The pressure head at the wetting front was calculated through an adjustment in the GAML model, considering the rate of stable infiltration (Tie) as representative of the hydraulic conductivity, and the transmission zone moisture instead of the moisture saturation. Once having the ψ m values and soil characteristics, regression models were adjusted, choosing the best fit by R 2 , significance of parameters, less number of variables and easy of obtaining soil variables. The soil hydraulic conductivity values, percentage of silt and macroporosity were all significant for all equations. Tie was not significant in none of the equations. All the obtained equations using the amount of silt in combination with another variable showed good results in the ψ m modeling. The best fitted equation was the one which related the ψ m with the porosity, the soil hydraulic conductivity and the percentage of silt.
Dissertação importada do Alexandria

Les composites à matrice céramique oxyde/oxyde peuvent être considérés pour des applications structurales opérant, en continu, sous environnement oxydant à des températures comprises entre 500°C et 900°C, comme c’est le cas dans les zones proches des moteurs d’avions. En particulier, les composites reposant sur une matrice associant de l’alumine et de la silice présentent un fort potentiel. En outre, la mise en œuvre de ces matériaux comprend plusieurs étapes dont deux sont essentielles : l’imprégnation du renfort fibreux par la suspension et le frittage de la matrice. Cette thèse s’intéresse à l’élaboration de composites à matrice céramique oxyde/oxyde utilisant une matrice alumine-silice. Celle-ci est issue d’une suspension aqueuse dans laquelle les deux espèces sont initialement présentes sous formes de particules. Aussi, l’objectif de ces travaux est d’étudier le comportement d’un tel système au cours des différentes étapes clés de la fabrication, c’est-à-dire d’établir les relations procédé/microstructure/propriétés, afin de proposer une composition optimale de la matrice au regard du procédé et des propriétés visées. En particulier, la proportion de silice sera un paramètre crucial. Tout d’abord, étant donné que la réussite de l’étape d’imprégnation repose sur la capacité de la suspension à s’écouler au sein de la structure fibreuse, une caractérisation rhéologique des suspensions d’oxydes a été menée. Le comportement rhéologique a été interprété sur la base des domaines de prédominance des différentes interactions au sein de la suspension. Aussi, l’influence des différentes caractéristiques des suspensions, comme la concentration volumique en particules et la proportion alumine-silice, a été examinée. Ensuite, le comportement de ce système au cours du frittage a été étudié puisque ce traitement thermique doit permettre, entre autres, d’aboutir à une microporosité respectueuse du concept de composites à matrice faible. Les mécanismes de frittage ont été identifiés tandis que l’influence des différents paramètres sur la cinétique a été qualifiée. Aussi, des liens avec les propriétés mécaniques de la matrice ont été établis. Enfin, des composites à renforts Nextel™ 610 et à matrice poreuse alumine-silice ont été mis en œuvre et caractérisés
Oxide/oxide ceramic matrix composites can be used for structural applications operating continuously at temperatures between 500°C and 900°C under oxidizing environments, such as in areas close to aircraft engines. In particular, composites based on a matrix combining alumina and silica are promising. In addition, the processing of these materials comprises several steps. Two of them are essential: the impregnation of the fibrous reinforcement with the suspension and the sintering of the matrix. This PhD thesis focuses on the processing of oxide/oxide ceramic matrix composites using an alumina-silica matrix. It is derived from an aqueous suspension in which the two species are initially present as particles. The aim of this work is to study the behaviour of such a system during the various stages of the manufacturing, i.e. to establish the relationships between processing/microstructure/properties, in order to propose an optimal composition of the matrix regarding the process and the required properties. In particular, the silica proportion will be a crucial parameter. Firstly, since the quality of the impregnation step is based on the ability of the suspension to flow within the fibrous structure, a rheological characterization of the oxide suspensions has been carried out. The rheological behavior has been interpreted on the basis of the domains of predominance of the different interactions within the suspension. Also, the influence of the various suspension characteristics, such as the solid fraction and the alumina-silica ratio, has been examined. Then, the behaviour of this system during the sintering has been studied since this thermal treatment should lead to a microporosity that respects the concept of weak matrix composites. The sintering mechanisms have been identified while the influence of the various parameters on the kinetics has been qualified. Also, relationships with the mechanical properties of the matrix have been established. Finally, composites with Nextel™ 610 reinforcements and a porous alumina-silica matrix have been fabricated and characterized

La fiabilite des materiaux composites a matrice d'alliage de titane renforces par des filaments de carbure de silicium etant tres directement liee a la stabilite de la zone interfaciale fibre/matrice, une approche predictive des mecanismes de rupture de cette zone de couplage entre constituants a ete proposee. Cette approche constitue une aide a la conception des materiaux composites en prenant en compte dans des modeles de fissuration associes a des simulations numeriques, des etats de contraintes residuelles d'origine thermomecanique et physico-chimique. La validite de cette approche dependant de la credibilite des caracteristiques thermoelastiques utilisees pour les phases en presence, des procedures experimentales permettant la caracterisation de depots de faible epaisseur sur substrats plans ou filamentaires ont ete mises au point

La fiabilite des materiaux composites a matrice d'alliage de titane renforces par des filaments de carbure de silicium etant tres directement liee a la stabilite de la zone interfaciale fibre/matrice, une approche predictive des mecanismes de rupture de cette zone de couplage entre constituants a ete proposee. Cette approche constitue une aide a la conception des materiaux composites en prenant en compte dans des modeles de fissuration associes a des simulations numeriques, des etats de contraintes residuelles d'origine thermomecanique et physico-chimique. La validite de cette approche dependant de la credibilite des caracteristiques thermoelastiques utilisees pour les phases en presence, des procedures experimentales permettant la caracterisation de depots de faible epaisseur sur substrats plans ou filamentaires ont ete mises au point

Les matériaux nanocomposites suscitent un intérêt grandissant en recherche dû au fait qu'ils améliorent les propriétés barrières en incorporant une faible quantité de nanocharges inférieure à 5%. Actuellement, les montmorillonites organiquement modifiées (MMT-O) sont les nanocharges les plus répandues grâce à leur rapport de forme élevé permettant de favoriser les interactions surfaciques argile/polymère. Si ces matériaux présentent d'excellentes performances, leur durabilité et l'impact de la présence d'argile dans la matrice polymère n'a pas encore été étudiée en profondeur. Notre objectif était d'étudier finement le comportement vis-à-vis de l'oxydation de nanocomposites à matrice polypropylène et polyéthylène non stabilisés afin de mettre en évidence les effets de l'argile sur le processus d'oxydation aux faibles températures Ces effets ont deux origines : une origine chimique et une origine physique. Pour étudier ces deux origines, une démarche expérimentale et de modélisation du processus d'oxydation contrôlée ou non par la diffusion d'oxygène (respectivement dégradation hétérogène et homogène) a été mise en place. D'une manière générale, il apparait que la présence de MMT-O accélère l'oxydation. Ce phénomène a été modélisé par l'ajout de réaction catalytique entre les particules métalliques initialement présentes dans la MMT-O et les hydroperoxydes liés à l'oxydation. Concernant l'effet de la MMT-O sur la perméabilité à l'oxygène, deux cas ont été observés : dans le cas du système à base polypropylène (morphologie intercalée/exfoliée), une diminution de 45% de perméabilité a été mesurée par rapport à la matrice seule, alors que dans le cas du système à base de polyéthylène (morphologie intercalée), pas de variation significative a été détectée. Les cinétiques et les profiles dans l'épaisseur des échantillons des produits d'oxydation ont été mesurés et simulés par un modèle couplant réactions d'oxydation et diffusion d'oxygène dans les deux systèmes. Dans le cas du système à matrice polyéthylène, les modifications induites par l'oxydation sur les masses molaires et sur la morphologie cristalline sont prédites. Enfin, en se basant sur des relations structure-propriétés, des profils de module mécanique ont été simulés dans le cas de la dégradation hétérogène (oxydation contrôlée par la diffusion). Ces simulations ont été confirmées par des mesures de modules dans l'épaisseur d'échantillons épais de nanocomposite à matrice polyéthylène oxydés
Nanocomposite materials attract search due to their improvements on barrier properties by incorporating low level of nanofiller of 5%w. Nowadays, organically modified montmorillonites (MMT-O) are the most used fillers due to their high aspect ratio which permits stronger clay/polymer interactions. If nanoreinforced materials are highly performing, the ways in which clay presence affects polyolefin durability have not being subject of a rigorous study, thus they are not yet clear. Our goal was to examine unstabilized clay polypropylene and unstabilized clay polyethylene nanocomposites to get a better comprehension of the clay effects on their thermooxidation process under low temperatures. The effects induced by a dual physic –chemical nature of the clay were explored. The problem was tackled from both experimental and theoretical point of views for degradation process not controlled and controlled by oxygen diffusion (homogenous and heterogeneous respectively). It seems that MMT-O speeds up oxidation. This phenomenon was modeled by adding a catalytic reaction between metallic particles initially present in the MMT-O and hydroperoxyde groups (main responsible of oxidation). Regarding the oxygen permeability two situations were confronted: for the clay polypropylene system a decrease of 45% of oxygen permeability was measured. On the other hand, no variation was found for the polyethylene case. This effect was attributed to the fact that polyethylene nanocomposite reached a blend morphology less developed than those of the polypropylene nanocomposite. Kinetics and oxidation products profiles across the sample thickness were simulated for both systems by coupling oxidation reactions with oxygen diffusion equations. For the polyethylene case, the effects induced by oxidation on molar mass and crystalline morphology were also simulated. Finally, based on structure – property relation, simulations of mechanic modulus profiles were performed for the heterogeneous degradation case (oxidation diffusion controlled). These results were confirmed by experimental measurements of modulus across the thickness of thick clay polyethylene nanocomposite samples

Les composites à matrice métallique renforces par des particules céramiques, pour lesquels la matrice et le renfort supportent la charge appliquée, sont de nos jours d'un intérêt industriel indéniable. Ils offrent comme avantages des propriétés relativement isotropes, un faible cout, une grande maniabilité et des performances significativement meilleures que celles des alliages non renforces constituant leur matrice. Mais avant de procéder à leur exploitation commerciale certaines caractéristiques restent a déterminer, notamment leur comportement en fatigue est un point crucial en vue d'application comme matériau de structure. Ainsi le but de ce travail est l'étude de l'influence du traitement mécanique de surface de galetage sur ces composites. Lorsqu'une phase céramique est finement dispersée dans une matrice métallique des contraintes résiduelles sont invariablement générées. Le premier objectif a été de mesurer dans les deux phases par diffraction aux rayons x l'évolution de ces contraintes après traitement thermique, galetage et fatigue. Dans le cas d'un alliage d'aluminium 2014 renforce par 15 pour-cent en volume de particules de carbure de silicium il a été trouvé que d'importantes pseudomacrocontraintes sont présentes après traitement thermique, que de fortes macrocontraintes de compression sont générées par galetage, et que le taux de relaxation de ces macrocontraintes dépend du signe du chargement de fatigue. Des résultats nouveaux concernant la répartition en surface et en profondeur des macro- et des pseudomacro-contraintes ont été obtenus après galetage et fatigue. Un parallèle avec la largeur du pic de diffraction et la dureté du matériau a été établi. Par ailleurs les courbes de Wohler du composite traite au maximum de dureté et ou non galeté indiquent un gain de 30 pour-cent en limite de fatigue attribuable au galetage. Une deuxième partie traite la modélisation du galetage qui a été décomposée en trois temps: détermination de la distribution de pression au niveau du contact conforme entre le galet et l'éprouvette, calcul des champs mécaniques a l'état stabilise par une méthode stationnaire directe et analyse de la répartition des contraintes résiduelles a l'échelle microscopique via un modèle d'éléments finis a hypothèses périodiques. Une étude paramétrique des champs résiduels macroscopiques a mis en valeur le rôle prépondérant joue par la loi de comportement et le coefficient de frottement. Les données numériques ont ensuite été comparées aux données expérimentales déterminées précedemment, montrant un bon accord en termes de couche affectée et de profil de macrocontraintes résiduelles

L'expression de genes cardiaques est une etape importante dans la comprehension de la reponse du myocarde a des conditions d'hypertension arterielle. La reexpression de formes dites ftales a ete bien demontree au niveau des cardiomyocytes. Nous presentons ici une etude de proteines de la matrice extra-cellulaire et des cellules musculaires lisses dans divers modeles de rat hypertendus. L'analyse par immunomarquage de proteines majeures de la matrice extra-cellulaire (fibronectine, collagene) a permis de demontrer qu'une surcharge de pression brutale induit l'accumulation precoce de la fibronectine (fn) qui precede celle de collagene. L'analyse par hybridation in situ demontre que les cellules interstitielles et des cellules musculaires lisses arterielles accumulent les arnm des isoformes ftales de la fn des la 24eme heure suivant l'imposition de la surcharge. Le phenotype des cellulaires musculaires lisses coronaires evolue donc d'un etat contractile vers un etat moins mature. Dans un cas d'hypertension arterielle maligne (rat spontanement hypertendu stroke-prone) la fn cellulaire s'accumule egalement dans la media des coronaires et au niveau des zones d'ischemie. Ce changement de phenotype des cellules musculaires lisses coronaires est associe a des modifications d'expression des proteines contractiles (expression de la chaine lourde de la myosine non musculaire) qui sont specifiques du type d'artere consideree (elastique ou musculaire) et de son calibre. Le phenotype des cellules musculaires lisses n'est pas correle au niveau de pression arterielle, mais influence le developpement des lesions ischemiques. L'ensemble de ce travail demontre que suite a une surcharge de pression, quelle que soit l'etiologie, le phenotype des cellules musculaires lisses, comme celui des cardiomyocytes evolue vers un type moins mature. La pression arterielle n'est pas le seul element responsable de ces changements phenotypiques. Le role de la matrice extra-cellulaire dans la regulation de l'expression des genes cardiaques est discute

I materiali (nano)compositi, unendo al loro interno le prestazioni dei loro componenti, che in alcuni casi possono addirittura agire sinergicamente sviluppando nuove proprietà non appartenenti alle singole fasi isolate, appaiono come una risposta ottimale alle nuove esigenze che richiedono materiali performanti dal punto di vista meccanico e sempre più dotati di funzionalità aggiuntive. È noto come l’uso di nanocariche consenta non solo di migliorare le proprietà meccaniche, ma di aggiungere proprietà funzionali di varia natura. In questo lavoro di tesi si sono quindi valutate due tipologie di nanocariche, grafene e organoclay (ritardante di fiamma), come modificatori di una matrice epossidica commerciale. La stessa matrice è stata utilizzata anche per produrre compositi contenenti fibra di carbonio riciclata da pirolisi, con la prospettiva futura di unire i processi e ottenere compositi da fibra di riciclo e matrice multifunzionale.

I nanocompositi sono una nuova classe di materiali che mostrano proprietà uniche tipicamente non condivise dai materiali convenzionali. La dispersione di particelle nanometriche, organiche o inorganiche, all’interno di una matrice polimerica può determinare l’incremento delle proprietà del composito e nel contempo può donare nuove proprietà funzionali. Il grosso interesse rivolto verso i nanocompositi dipende dalle potenzialità che tali materiali mostrano e dalle possibili applicazioni che essi possono trovare. Film rigidi o flessibili in nanocomposito, troverebbero applicazione nel packaging, vista la tendenza a conservare la trasparenza della matrice e le proprietà di impermeabilità all’ossigeno che l’utilizzo di nanocariche può determinare. Nel presente lavoro è stata messa a punto una rapida procedura di fabbricazione di film spessi in nanocomposito poliestere-montmorillonite per consentirne un’applicazione industriale. Le proprietà dinamo-meccaniche dei film sono state valutate tramite test al DMA, svolti nella particolare configurazione di trazione. I risultati ottenuti da tale prova hanno consentito di studiare la complessità dell’interazione tra nanocariche e matrice. I coatings sono spesso utili per diverse applicazioni ingegneristiche, da coating resistenti al graffio a coating che fungono da barriera termica. Poiché danni superficiali o all’interfaccia con il subtrato, possono influenzare le prestazioni finali, è importante adottare una buona tecnica di caratterizzazione per i coating. Le più recenti pubblicazioni scientifiche, a tal proposito, parlano di nanoindentazione di coating o bulk in nanocomposito. In questo lavoro viene utilizzata la tecnica di macro-indentazione strumentata per la caratterizzazione meccanica di coating, in nanocomposito poliestere-montmorillonite, depositati per spin coating su substrati in alluminio e polietilene ad alta densità. La macro-indentazione è meno sensibile alle intrinseche inomogeneità dei nanocompositi è da utili informazioni circa la resistenza dei coating. In più, in questo caso, la preparazione del campione può essere meno accurata rispetto al caso della nanoindentazione. Nell’appendice, è riportato un esempio di applicazione di macroindentazione per la caratterizzazione meccanica di materiale polimerico. In particolare il test consentiva di valutare l’effetto del contenuto locale di rinforzo in materiali polimerici caricati a gradiente. Dopo lo studio di film e coating in nanocomposito, è stato studiato il comportamento di nanocompositi nella forma di bulk. Provini bulk possono mostrare diverse proprietà rispetto ad i coating, in più, lo studio del comportamento del materiale di campioni bulk risulta più semplice e consente di approfondire alcuni aspetti. La combinazione di nanoparticelle e di una nuova tecnologia di schiumatura ha generato una nuova classe di materiali leggeri, ad alta resistenza e multifunzionali: le schiume in nanocomposito. Attualmente, risulta di grossa utilità trovare nuove, veloci ed economiche tecnologie che consentano di realizzare nanocompositi su larga scala. E’ stata sviluppata una nuova tecnologia di schiumatura per materiali termoindurenti che non richiede l’utilizzo di agenti esterni e che è stata chiamata di schiumatura allo stato solido. L’utilizzo di questa nuova tecnologia è stata utilizzata per la realizzazione di schiume nanocaricate. Lo sviluppo di materiali polimerici per applicazioni strutturali o tribolgiche, sta divenendo una domanda sempre più pressante. I compositi a matrice polimerica hanno le potenzialità per essere utilizzati per questo tipo di applicazioni; componenti in polimero, come camme, alberi e ruote dentate, sono tipicamente realizzati mediante la tecnologia dello stampaggio ad iniezione. Ciò è dovuto alla semplicità ed al basso costo di tale tecnologia che consente la realizzazione di componenti anche a geometria complessa. Tuttavia l’effetto del processo di stampaggio ad iniezione sulle proprietà di bulk di nanocompositi polimerici è ancora oggetto di studio. Nel presente lavoro, sono state studiate le proprietà tribologiche e meccaniche di di nanocompositi a matrice polimerica (PA6, PA66 and POM) , prodotti per stampaggio ad iniezione.
Nanocomposites are a relatively new class of materials with unique properties typically not shared by conventional microcomposites. The dispersion of nanometric organic or ingorganic particles in polymer matrix, may cause an increase in performances of composite materials and give new functional properties. The interest in polymer nanocomposites depends on the potential applications of these materials. Dealing with flexible or rigid films, packaging is a potential application because of the material transparency and the oxygen-barrier properties. In the present work, dynamic mechanical properties of polyester–montmorillonite nanocomposite thick films, prepared by the in situ intercalative polymerization method, were evaluated in a tensile mode. A fast fabrication procedure was chosen according to industrial applications and tensile DMA results permitted to study the interaction between nanofiller and matrix. Surface coatings are used in different engineering applications, from scratch-resisting coatings to thermal barriers. Nanocomposites have the potential for being high-performance coatings. As surface damage and interfacial failure may affect the final coating performances, the reliable characterisation of the coated film strength is critical. Recent scientific contributions mainly deal with the nanoindentation of nanocomposite coatings or bulk materials. In this work the use of instrumented macro-indentation is suggested for mechanical characterization of polyester–montmorillonite nanocomposite coatings deposited on aluminium and high-density polyethylene substrates by the spin coating method. Macro-indentation is less sensitive to material non-homogeneities and provides reliable information about the coating strength. Moreover, the sample preparation is less critical than for nanoindentation. In the appendix a particular instance of the use of macroindentation test is reported, instrumented macroindentation test was used to measure the effect of the local filler content in polymer functional graded materials . After the study of nanocomposite coatings and films, the study of bulk nunocomposites was performed to investigate the material beahviour. In fact, bulk samples exhibit different properties than coatings, moreover the study of bulk materials is easier and allow to deepen several scientific aspects. The combination of functional nanoparticles and foaming technology has generated a new class of lightweight, high strength, and multifunctional materials: the nanocomposite foams. Nowadays, the challenge is to find new fast and cheap production processes that are able to provide complex nanocomposite structures on a large scale. A new foaming technology called ‘solid-state foaming’ has recently been developed to foam thermosetting materials without using any external agent. This new technology is very easy and special equipments are not necessary. In the present work, this method was used for fabricating nanocomposite foams. Nowadays, the development of advanced materials for tribological purposes is becoming a pressing demand of manufacturing industries. Polymer-based composites have the capability of operating for a long time without lubrication in conditions of cryogenic and elevated temperatures. Components, such as gears and cams are typically produced by injection molding of thermoplastic matrix composites. In fact, the ease and economics of manufacturing complex parts by injection molding are well recognized, but the effect of the injection molding process on the bulk properties of nanocomposites is still under investigation. In this study, the author evaluated the tribological and mechanical behavior of neat and nanofilled functional polymers (PA6, PA66 and POM) produced by injectiono moulding.

L’attività di ricerca svolta è stata focalizzata sullo studio e la realizzazione di Materiali Autodiagnosticanti: ovvero materiali con la duplice funzione strutturale e di sensore. I materiali scelti per questo scopo sono compositi a matrice polimerica, dato il loro vasto campo applicativo e la loro grande versatilità. Il materiale realizzato consta di due parti fondamentali: il rinforzo strutturale costituito da fibre di vetro in resina epossidica e l’elemento sensibile costituito da una fase elettricamente conduttrice in carbonio in forma di fibre lunghe unidirezionali o nanoparticelle o nanofibre disperse nella resina epossidica. I compositi ibridi, realizzati in forma di tondini mediante un processo di pultrusione manuale, sono costituiti dall’elemento sensibile interno coassialmente rivestito di vetroresina. In tutti i casi l’efficienza dell’autodiagnosi è stata valutata correlando la variazione di resistenza elettrica della fase conduttrice con il carico e/o la deformazione applicati all’intero composito. Per ciascun tipo di elemento sensibile sono stati indagati aspetti precisi: 1. nel caso degli elementi sensibili in fibra di carbonio unidirezionali ci si è particolarmente soffermati sull’influenza della quantità di vetro esterna sulle proprietà di autodiagnosi; 2. nei provini con elementi sensibili realizzati con nano-particelle e nanofibre di carbonio in resina epossidica si è indagato l’effetto della tipologia di particelle impiegate (area superficiale, dimensione, aspect ratio, ecc.) sulle proprietà di conducibilità elettrica e di autodiagnosi. I risultati dei sensori con fibra di carbonio hanno evidenziato che questo tipo di materiale non è particolarmente adatto ad una funzione di monitoraggio continuo della sollecitazione, bensì ha interessanti applicazioni quale “sensore di guardia” con comportamento tipo “on-off”. Ciò a causa del particolare meccanismo di conduzione che consente sempre un cospicuo passaggio di corrente fino alla rottura delle fibre di carbonio. La ricerca ha evidenziato che tale comportamento di guardia può essere influenzato dalla quantità di vetro che riveste l’elemento sensibile. In particolare, l’attivazione del segnale di guardia (resistenza elettrica pari ad infinito) può essere anticipato rispetto alla rottura finale del composito aumentando la quantità di vetro. I sensori realizzati con nanoparticelle di carbonio hanno invece mostrato grande capacità di monitoraggio in continuo, e ciò a causa del fatto che in questi sistemi la conducibilità elettrica è associata ad un modello percolativo. All’aumentare del carico (e quindi della deformazione) del materiale, le particelle conduttrici vengono progressivamente allontanate le une dalle altre consentendo di registrare un graduale e continuo aumento della resistenza elettrica. In questi sistemi, tuttavia, la natura, morfologia, dimensione, area superficiale, ecc. delle nano-particelle influenzando notevolmente la formazione del network percolativo, influenzano conseguentemente anche le proprietà di autodiagnosi. Le particelle ad elevata area superficiale hanno mostrato le migliori proprietà di autodiagnosi. Nel passaggio dalle nanoparticelle alle nano-fibre di carbonio non ha portato i miglioramenti attesti. Questo particolare sistema è stato indagato in quanto consente teoricamente di ottenere buona conducibilità elettrica con minore quantitativo di carica grazie all’elevato aspect ratio delle nanofibre, tuttavia la manifattura degli elementi sensibili è risultata estremamente complessa. Le nanofibre commerciali, infatti, vengono fornite in forma di aggregati micrometrici e che necessitano lunghe manipolazioni con solventi per essere disaggregati. Tali operazioni, possibili con limitate quantità di materiale, sono invece molto difficoltose e delicate quando applicate a sistemi più grandi quali la pultrusione impiegata per realizzare i materiali di questa sperimentazione. I sensori ottenuti in nano fibra di carbonio, frutto di un compromesso tra il livello di dispersione delle nanofibre nella resina e la processabilità, hanno dimostrando proprietà di autodiagnosi molto simili a quelle delle particelle di carbonio con area superficiale bassa, assai poco soddisfacenti. I materiali risultati più idonei alle funzioni di autodiagnosi, ovvero quelli con elemento sensibile in nanoparticelle di carbonio ad elevata area superficiale, sono stati poi provati in condizioni pratiche di esercizio, quali rinforzi strutturali in travi di calcestruzzo. I risultati hanno mostrato che i materiali realizzati conservano le proprietà di autodiagnosi sotto carico anche se inseriti in sistemi massivi come il calcestruzzo e che, inoltre, grazie alla loro sensibilità è stato possibile monitorarne anche la fase di presa ed indurimento.
The research carried out was focused on the study and production of Composite Smart Material: materials with the dual function: structural and sensor. The materials chosen for this purpose are polymer matrix composites, due to their vast application field and their versatility. The material produced consists of two basic parts: the structural reinforcement consists of glass fibers in epoxy resin and the sensible element consists of a phase-sensitive electrically conductive carbon in the form of unidirectional long fibers or nanoparticles or nanofibers dispersed in epoxy resin. The hybrid composite, realized in the form of rods by a process of pultrusion manual, consisting of the element sensitive internal coaxially coated fiberglass. In all cases the efficiency of smart properties was assessed by correlating the change in electrical resistance of the phase conductor with the load and / or deformation applied to the entire composite. For each type of sensor element have been investigated specific aspects: 1. in the case of sensitive elements in carbon fiber unidirectional one is particularly dwelt on the influence of the amount of exterior glass on the properties of self-diagnosis; 2. in samples with sensitive elements made of nano-particles and carbon nanofibers in epoxy resin was investigated the effect of the type of particles used (surface area, size, aspect ratio, etc..) on the properties of electrical conductivity and self-diagnosis. The results of the sensors with carbon fiber have shown that this type of material is not particularly suitable for continuous monitoring function of the stress, but has interesting applications such as "Sensor Guard" behavior such as "on-off". This is because of the particular mechanism that allows always run a large current passing through rupture of carbon fibers. Research has shown that this behavior may be influenced guard by the amount of glass that covers the sensing element. In particular, the activation of the signal call (electrical resistance equal to infinity) may be faster than the final break of the composite by increasing the amount of glass. The sensors made of carbon nanoparticles have shown great ability but continuous monitoring owing to the fact that in these systems, the electrical conductivity is associated with a percolation model. Increasing load (ie deformation) of the material, the conductive particles are gradually removed from each other allowing you to record a gradual and continuous increase in electrical resistance. In these systems, however, the nature, morphology, size, surface area, etc.. of nano-particles significantly influence the formation of the percolation network, thus also affecting the properties of self-diagnosis. Particles with high surface area showed the best properties of self-diagnosis. In the transition from nanoparticles to nano-carbon fibers did not lead to improvements attests. This particular system has been investigated theoretically since it allows to obtain good electrical conductivity with less quantity of charge thanks to the high aspect ratio of nanofibers, but the manufacturing of the sensing elements was extremely complex. The nanofibers trade, in fact, is provided in the form of aggregated micro and requiring lengthy manipulations with solvents to be broken. Such operations, possibly with small amounts of material, are very difficult and sensitive when applied to larger systems such as pultrusion designed to produce the materials of this trial. The sensors obtained in nano carbon fiber, a compromise between the degree of dispersion of nanofibers in the resin and processability, showed properties very similar to the self of carbon particles with low surface area, not very satisfactory. The materials are more appropriate to the functions of self-diagnosis or those with sensitive element in nanoparticles of carbon with high surface area, were then tested in practical conditions of operation, such as structural reinforcement in concrete beams. The results showed that the materials remain the property of self-made load even if incorporated into systems such as the massive concrete and that, furthermore, due to their sensitivity has been possible to also monitor the stage setting and hardening.