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Vector interpretation of the matrix orthogonality on the real line

Branquinho, A.; Marcellán, F.; Mendes, A.
Fonte: Centro de Matemática da Universidade de Coimbra Publicador: Centro de Matemática da Universidade de Coimbra
Tipo: Pré-impressão
ENG
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55.48%
In this paper we study sequences of vector orthogonal polynomials. The vector orthogonality presented here provides a reinterpretation of what is known in the literature as matrix orthogonality. These systems of orthogonal polynomials satisfy three-term recurrence relations with matrix coefficients that do not obey to any type of symmetry. In this sense the vectorial reinterpretation allows us to study a non-symmetric case of the matrix orthogonality. We also prove that our systems of polynomials are indeed orthonormal with respect to a complex measure of orthogonality. Approximation problems of Hermite-Pad´e type are also discussed. Finally, a Markov’s type theorem is presented.

The matrix-tolerance hypothesis: an empirical test with frogs in the Atlantic Forest

DIXO, Marianna; METZGER, Jean Paul
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
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55.53%
The matrix-tolerance hypothesis suggests that the most abundant species in the inter-habitat matrix would be less vulnerable to their habitat fragmentation. This model was tested with leaf-litter frogs in the Atlantic Forest where the fragmentation process is older and more severe than in the Amazon, where the model was first developed. Frog abundance data from the agricultural matrix, forest fragments and continuous forest localities were used. We found an expected negative correlation between the abundance of frogs in the matrix and their vulnerability to fragmentation, however, results varied with fragment size and species traits. Smaller fragments exhibited stronger matrix-vulnerability correlation than intermediate fragments, while no significant relation was observed for large fragments. Moreover, some species that avoid the matrix were not sensitive to a decrease in the patch size, and the opposite was also true, indicating significant differences with that expected from the model. Most of the species that use the matrix were forest species with aquatic larvae development, but those species do not necessarily respond to fragmentation or fragment size, and thus affect more intensively the strengthen of the expected relationship. Therefore...

O ansatz do produto matricial: uma nova abordagem para modelos exatamente solúveis; The matrix product ansatz: a new formulation far the exact soluble

Lazo, Matheus Jatkoske
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 14/03/2006 PT
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Neste trabalho mostramos que uma grande variedade de modelos exatamente solúveis através do ansatz de Bethe coordenadas podem também ser resolvidos através de um ansatz do produto matricial. Estes modelos são descritos no caso unidimensional por cadeias quânticas, e por matrizes de transferência no caso de sistemas clássicos bi-dimensionais. Diferentemente do ansatz de Bethe, em que as auto-funções do modelo são escritas como uma combinação de ondas planas, no nosso ansatz do produto matricial elas são dadas por produtos de matrizes, onde as matrizes obedecem a uma álgebra associativa apropriada. Estas relações algébricas são obtidas impondo-se que as auto-funções escritas em termos do ansatz satisfaçam à equação de auto-valor do operador Hamiltoniano ou da matriz de transferência. A consistência das relações de comutatividade entre os elementos da álgebra implicam na exata integrabilidade do modelo. Além disso, o ansatz que propomos permite uma formulação simples e unificada para vários Hamiltonianos quânticos exatamente solúveis. Apresentamos nesta tese a formulação do nosso ansatz do produto matricial para uma grande família de redes quânticas, como os modelos anisotrópico de Heisenberg, Fateev-Zamolodchikov...

Influence of Cu and Cr on the matrix decomposition of quenched Al-Zn-Mg alloy

Lourenco, C. Dos Santos; Cilense, M.; Garlipp, W.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica
ENG
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55.45%
The Inoue procedure is used to study the influence of Cr and Cu elements, jointly or individually, on the matrix decomposition of quenched Al-Zn-Mg alloys. The addition of copper and copper with chromium does not significantly change the limits of the temperatures of formation of Guinier-Preston zone and the range of the matrix decomposition. The control of the vacancy concentration in the alloys by different heat treatments and the addition of certain elements such as copper and chromium seems to play an important role in the nucleation rate and the kinetics of phase transformations.

Influência de polimorfismos genéticos sobre os níveis circulantes das metaloproteinases de matriz extracelular 2 e 9 durante hemodiálise = : Influence of genetic polymorphisms on the circulating levels of the matrix metalloproteinases 2 and 9 during hemodialysis; Influence of genetic polymorphisms on the circulating levels of the matrix metalloproteinases 2 and 9 during hemodialysis

Bernardo Pavinato Marson
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/07/2012 PT
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A insuficiência renal crônica é uma complicação grave de diferentes doenças, como diabetes, hipertensão e glomerulopatias. Quando os rins entram em falência, é preciso substituir a função renal, terapia geralmente feita através de hemodiálise. A população de pacientes dependentes de hemodiálise, cujo número cresce de forma geométrica, está exposta a taxas extremamente elevadas de eventos cardiovasculares fatais e não fatais. Fatores de risco clássicos e específicos da uremia se somam conferindo alterações patológicas severas na parede dos vasos. A própria sessão de hemodiálise ativa a inflamação e induz aterogênese. A degradação da elastina e a apoptose das células musculares lisas evoluem para a mudança do fenótipo da camada média, que se expande reduzindo o lúmem em um processo de acentuada calcificação arterial. Alterações na atividade das metaloproteinases de matriz extracelular (MMPs) 2 e 9 e desequilíbrios com seus inibidores endógenos, os TIMPs, ajudam a compor este cenário ao estimular o remodelamento cardiovascular e reorganizar a matriz extracelular, permitindo a expansão tecidual e o depósito de cálcio. Os níveis circulantes de MMP-2 e -9 estão relacionados com maior severidade de doenças cardiovasculares na hemodiálise. Diversos polimorfismos genéticos foram associados com alterações na concentração e/ou atividade destas enzimas...

Blocked schur algorithms for computing the matrix square root

Deadman, Edvin; Higham, Nicholas J.; Ralha, Rui
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
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55.5%
The Schur method for computing a matrix square root reduces the matrix to Schur triangular form and then computes a square root of the triangular matrix. We show that by using either a standard blocking or recursive blocking the computation of the square root of the triangular matrix can be made rich in matrix multiplication. Numerical experiments making appropriate use of level 3 BLAS show significant speedups over the point algorithm, both in the square root phase and in the algorithm as a whole. In parallel implemetnations, recursive blocking is found to provide better performance than standard blocking when parallelism comes only from threaded BLAS, but the reverse is true when parallelism is explicitly expressed using OpenMP. The excellent numerical stability of the point algorithm is shown to be preserved by blocking. These results are extended to the real Schur method. Blocking is also shown to be effective for multiplying triangular matrices.

The Matrix: a aventura da formação no mundo tecnologizado

Silva,Flávio Caetano da
Fonte: Centro de Estudos Educação e Sociedade - Cedes Publicador: Centro de Estudos Educação e Sociedade - Cedes
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2007 PT
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O artigo se inscreve na intersecção entre a educação e a produção fílmica. O argumento propõe reflexões sobre a educação escolar e as formas de controle exercido no cotidiano de alunos, professores e gestores a partir de instigantes provocações que o filme The Matrix, o primeiro da trilogia, nos oferece. Nosso interesse está nas práticas escolares de institucionalização dos sujeitos, produzindo realidades inevitáveis. Os sujeitos são produzidos através de discursos sofisticados, mediados pelas novas tecnologias de comunicação e informação. Nos propomos a discutir tanto as formas de controle do pensamento e de sua produção, quanto a própria possibilidade de realizar percursos no interior do roteiro de um filme, considerando as tramas de seu enredo. Estabelecemos uma leitura exploratória da construção do herói dostoievskiano para superar uma leitura superficial e fatalista, possível naquele filme.

Membrane Potential-Driven Protein Import into Mitochondria: The Sorting Sequence of Cytochrome b2 Modulates the Δψ-Dependence of Translocation of the Matrix-targeting Sequence

Geissler, Andreas; Krimmer, Thomas; Bömer, Ulf; Guiard, Bernard; Rassow, Joachim; Pfanner, Nikolaus
Fonte: The American Society for Cell Biology Publicador: The American Society for Cell Biology
Tipo: Artigo de Revista Científica
Publicado em /11/2000 EN
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The transport of preproteins into or across the mitochondrial inner membrane requires the membrane potential Δψ across this membrane. Two roles of Δψ in the import of cleavable preproteins have been described: an electrophoretic effect on the positively charged matrix-targeting sequences and the activation of the translocase subunit Tim23. We report the unexpected finding that deletion of a segment within the sorting sequence of cytochrome b2, which is located behind the matrix-targeting sequence, strongly influenced the Δψ-dependence of import. The differential Δψ-dependence was independent of the submitochondrial destination of the preprotein and was not attributable to the requirement for mitochondrial Hsp70 or Tim23. With a series of preprotein constructs, the net charge of the sorting sequence was altered, but the Δψ-dependence of import was not affected. These results suggested that the sorting sequence contributed to the import driving mechanism in a manner distinct from the two known roles of Δψ. Indeed, a charge-neutral amino acid exchange in the hydrophobic segment of the sorting sequence generated a preprotein with an even better import, i.e. one with lower Δψ-dependence than the wild-type preprotein. The sorting sequence functioned early in the import pathway since it strongly influenced the efficiency of translocation of the matrix-targeting sequence across the inner membrane. These results suggest a model whereby an electrophoretic effect of Δψ on the matrix-targeting sequence is complemented by an import-stimulating activity of the sorting sequence.

Overexpression of the Matrix Metalloproteinase Matrilysin Results in Premature Mammary Gland Differentiation and Male Infertility

Rudolph-Owen, Laura A.; Cannon, Paul; Matrisian, Lynn M.
Fonte: The American Society for Cell Biology Publicador: The American Society for Cell Biology
Tipo: Artigo de Revista Científica
Publicado em /02/1998 EN
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To examine the role of matrilysin (MAT), an epithelial cell-specific matrix metalloproteinase, in the normal development and function of reproductive tissues, we generated transgenic animals that overexpress MAT in several reproductive organs. Three distinct forms of human MAT (wild-type, active, and inactive) were placed under the control of the murine mammary tumor virus promoter/enhancer. Although wild-type, active, and inactive forms of the human MAT protein could be produced in an in vitro culture system, mutations of the MAT cDNA significantly decreased the efficiency with which the MAT protein was produced in vivo. Therefore, animals carrying the wild-type MAT transgene that expressed high levels of human MAT in vivo were further examined. Mammary glands from female transgenic animals were morphologically normal throughout mammary development, but displayed an increased ability to produce β-casein protein in virgin animals. In addition, beginning at approximately 8 mo of age, the testes of male transgenic animals became disorganized with apparent disintegration of interstitial tissue that normally surrounds the seminiferous tubules. The disruption of testis morphology was concurrent with the onset of infertility. These results suggest that overexpression of the matrix-degrading enzyme MAT alters the integrity of the extracellular matrix and thereby induces cellular differentiation and cellular destruction in a tissue-specific manner.

Activities of the Matrix Metalloproteinase Stromelysin-2 (MMP-10) in Matrix Degradation and Keratinocyte Organization in Wounded Skin

Krampert, Monika; Bloch, Wilhelm; Sasaki, Takako; Bugnon, Philippe; Rülicke, Thomas; Wolf, Eckhard; Aumailley, Monique; Parks, William C.; Werner, Sabine
Fonte: The American Society for Cell Biology Publicador: The American Society for Cell Biology
Tipo: Artigo de Revista Científica
Publicado em /12/2004 EN
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55.49%
The matrix metalloproteinase stromelysin-2 is expressed in keratinocytes of the epithelial tongue of skin wounds, suggesting a role in keratinocyte migration. Here, we show that stromelysin-2 enhances migration of cultured keratinocytes. To gain insight into the in vivo activities of stromelysin-2 in epithelial repair, we generated transgenic mice expressing a constitutively active stromelysin-2 mutant in keratinocytes. These animals had no alterations in skin architecture, and the healing rate of skin wounds was normal. Histologically, however, we found abnormalities in the organization of the wound epithelium. Keratinocytes at the migrating epidermal tip were scattered in most sections of mice with high expression level, and there was a reduced deposition of new matrix. In particular, the staining pattern of laminin-5 at the wound site was altered. This may be due to proteolytic processing of laminin-5 by stromelysin-2, because degradation of laminin-5 by this enzyme was observed in vitro. The inappropriate matrix contact of keratinocytes was accompanied by aberrant localization of β1-integrins and phosphorylated focal adhesion kinase, as well as by increased apoptosis of wound keratinocytes. These results suggest that a tightly regulated expression level of stromelysin-2 is required for limited matrix degradation at the wound site...

The matrix protein CCN1 (CYR61) induces apoptosis in fibroblasts

Todorovicç, Viktor; Chen, Chih-Chiun; Hay, Nissim; Lau, Lester F.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 07/11/2005 EN
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55.48%
Integrin-mediated cell adhesion to extracellular matrix proteins is known to promote cell survival, whereas detachment from the matrix can cause rapid apoptotic death in some cell types. Contrary to this paradigm, we show that fibroblast adhesion to the angiogenic matrix protein CCN1 (CYR61) induces apoptosis, whereas endothelial cell adhesion to CCN1 promotes cell survival. CCN1 induces fibroblast apoptosis through its adhesion receptors, integrin α6β1 and the heparan sulfate proteoglycan (HSPG) syndecan-4, triggering the transcription-independent p53 activation of Bax to render cytochrome c release and activation of caspase-9 and -3. Neither caspase-8 activity nor de novo transcription or translation is required for this process. These results show that cellular interaction with a specific matrix protein can either induce or suppress apoptosis in a cell type–specific manner and that integrin α6β1-HSPGs can function as receptors to induce p53-dependent apoptosis.

VESICLES ASSOCIATED WITH CALCIFICATION IN THE MATRIX OF EPIPHYSEAL CARTILAGE

Anderson, H. Clarke
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/04/1969 EN
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55.49%
Vesicles have been identified within the cartilage matrix of the upper tibial epiphyseal plate of normal mice. They were seen at all levels within the plate and usually did not appear to be in contact with cartilage cells. Vesicles were concentrated within the matrix of the longitudinal septa from the proliferative zone downward. They varied considerably in size (∼300 A to ∼1 µ) and in shape. They were bounded by unit membranes, and contained materials of varying density including, rarely, ribosomes. A close association was demonstrated between matrix vesicles and calcification: in the lower hypertrophic and calcifying zones of the epiphysis, vesicles were found in juxtaposition to needle-like structures removed by demineralization with ethylenediaminetetraacetate and identified by electron diffraction as hydroxyapatite and/or fluorapatite crystal structure—the former being indistinguishable from the latter for most cases in which electron diffraction methods are employed. Decalcification also revealed electron-opaque, partially membrane-bounded structures within previously calcified cartilage of the epiphyseal plate and underlying metaphysis which corresponded in size and distribution to matrix vesicles. It is suggested that matrix vesicles are derived from cells and that they may play a role in initiating calcification at the epiphysis.

Pay32p of the yeast Yarrowia lipolytica is an intraperoxisomal component of the matrix protein translocation machinery

Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 02/12/1995 EN
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55.47%
Pay mutants of the yeast Yarrowia lipolytica fail to assemble functional peroxisomes. One mutant strain, pay32-1, has abnormally small peroxisomes that are often found in clusters surrounded by membraneous material. The functionally complementing gene PAY32 encodes a protein, Pay32p, of 598 amino acids (66,733 D) that is a member of the tetratricopeptide repeat family. Pay32p is intraperoxisomal. In wild-type peroxisomes, Pay32p is associated primarily with the inner surface of the peroxisomal membrane, but approximately 30% of Pay32p is localized to the peroxisomal matrix. The majority of Pay32p in the matrix is complexed with two polypeptides of 62 and 64 kD recognized by antibodies to SKL (peroxisomal targeting signal-1). In contrast, in peroxisomes of the pay32-1 mutant, Pay32p is localized exclusively to the matrix and forms no complex. Biochemical characterization of the mutants pay32-1 and pay32-KO (a PAY32 gene disruption strain) showed that Pay32p is a component of the peroxisomal translocation machinery. Mutations in the PAY32 gene prevent the translocation of most peroxisome-bound proteins into the peroxisomal matrix. These proteins, including the 62-kD anti-SKL-reactive polypeptide, are trapped in the peroxisomal membrane at an intermediate stage of translocation in pay32 mutants. Our results suggest that there are at least two distinct translocation machineries involved in the import of proteins into peroxisomes.

INCREASED FIXATION OF SULFUR35 BY CARTILAGE IN VITRO FOLLOWING DEPLETION OF THE MATRIX BY INTRAVENOUS PAPAIN

McElligott, T. F.; Potter, J. L.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 31/10/1960 EN
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The uptake in vitro of sulfur-35 by costal cartilage obtained from nine rabbits 11 days after an intravenous injection of crude papain solution was compared with that in costal cartilage from eight normal untreated rabbits. An increased fixation of the isotope was found in treated animals compared with controls. The depletion of cartilage matrix by papain provided an experimental situation to test the hypothesis that the depletion of matrix which occurs in osteoarthritic cartilage can stimulate increased synthesis of chondroitin sulfate. The results give further support to the view that the primary lesion in osteoarthritis occurs in the matrix rather than in the chondrocyte of articular cartilage.

Correlation between Sweet Spots of Glycopeptides and Polymorphism of the Matrix Crystal in MALDI Samples

Nishikaze, Takashi; Okumura, Hisako; Jinmei, Hiroshi; Amano, Junko
Fonte: The Mass Spectrometry Society of Japan Publicador: The Mass Spectrometry Society of Japan
Tipo: Artigo de Revista Científica
EN
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A standard dried-droplet preparation using 2,5-dihydroxybenzoic acid (2,5-DHBA) as the matrix results in a large variation in signal intensity and poor shot-to-shot reproducibility in matrix-assisted laser desorption/ionization (MALDI). We expected that the differences can be attributed to the nature of the crystal structures in the region of the “sweet spot” within the MALDI samples. 2,5-DHBA crystals with and without analytes on a target plate obtained by means of a dried-droplet preparation contain two polymorphs, which can be distinguished by Raman spectra. In comparing the Raman image with the MS image, a clear correlation between the signal distribution of glycopeptides and hydrophilic peptides and the specific crystal form of 2,5-DHBA could be made. The ionization of hydrophobic peptides appears to proceed in both types of polymorphic crystals. In addition, the derivatization of glycopeptides with a pyrene group enabled us to detect glycopeptides regardless the crystal form. As the result, the number of sweet spots increased and MS spectra with a high signal intensity were obtained. The results suggest that the introduction of a hydrophobic/aromatic moiety to glycopeptides results in a more successful MALDI analysis due to the effective incorporation of the analyte into matrix crystals.

Time-resolved Analysis of the Matrix Metalloproteinase 10 Substrate Degradome*

Schlage, Pascal; Egli, Fabian E.; Nanni, Paolo; Wang, Lauren W.; Kizhakkedathu, Jayachandran N.; Apte, Suneel S.; Keller, Ulrich auf dem
Fonte: The American Society for Biochemistry and Molecular Biology Publicador: The American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
EN
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55.41%
Proteolysis is an irreversible post-translational modification that affects intra- and intercellular communication by modulating the activity of bioactive mediators. Key to understanding protease function is the system-wide identification of cleavage events and their dynamics in physiological contexts. Despite recent advances in mass spectrometry-based proteomics for high-throughput substrate screening, current approaches suffer from high false positive rates and only capture single states of protease activity. Here, we present a workflow based on multiplexed terminal amine isotopic labeling of substrates for time-resolved substrate degradomics in complex proteomes. This approach significantly enhances confidence in substrate identification and categorizes cleavage events by specificity and structural accessibility of the cleavage site. We demonstrate concomitant quantification of cleavage site spanning peptides and neo-N and/or neo-C termini to estimate relative ratios of noncleaved and cleaved forms of substrate proteins. By applying this strategy to dissect the matrix metalloproteinase 10 (MMP10) substrate degradome in fibroblast secretomes, we identified the extracellular matrix protein ADAMTS-like protein 1 (ADAMTSL1) as a direct MMP10 substrate and revealed MMP10-dependent ectodomain shedding of platelet-derived growth factor receptor alpha (PDGFRα) as well as sequential processing of type I collagen. The data have been deposited to the ProteomeXchange Consortium with identifier PXD000503.

Does the Matrix Matter? A Comparison on Phenology and Habitat utilization of Two Treefrog Species in the Big Cypress National Preserve

Isola, Monica
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
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Habitat loss and fragmentation are some of the causes of biodiversity decline. Naturally fragmented landscapes serve as analogues to anthropogenically fragmented landscapes. Recent studies have shown that the matrix between patches has an important role in the dynamics of patch-dwelling species. I studied phenology and habitat utilization of Hyla cinerea and Hyla squirella, the two most common yet understudied frogs, in two patchy landscapes of the Big Cypress National Preserve. Frogs were sampled in five domes and in their adjacent matrix, monthly, between 2006 and 2008. Using nighttime visual encounter surveys, specimens encountered were identified to species, and perch type, perch height and capture location were recorded. Analysis showed differences in abundance and habitat use patterns between patches and matrices for the two species across the two landscapes. These differences indicate that the matrix is important in shaping patterns of abundance and habitat use in fragmented landscapes.

A Simple Carrier-Based Modulation for the SVM of the Matrix Converter

GRUSON, François; LE MOIGNE, Philippe; DELARUE, Philippe; VIDET, Arnaud; CIMETIERE, Xavier; ARPILLIERE, Michel
Fonte: IEEE Transaction on Industrial Informatics Publicador: IEEE Transaction on Industrial Informatics
EN
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55.5%
Today, industry has not fully embraced the matrix converter solution. One important reason is its high control complexity. It is therefore relevant to propose a simpler but efficient modulation scheme, similar as three phase voltage source inverter modulators with the well-known symmetrical carrier-based ones. The modulation presented in this paper is equivalent to a particular space vector modulation (SVM) and takes into account harmonics and unbalanced input voltages, with the same maximum voltage transfer ratio (86%). The aim of this work is to propose a simple and general pulse width-modulation method using carrier-based modulator for an easier matrix converter control. Furthermore, a simple duty cycle calculation method is used, based on a virtual matrix converter. Finally, simulations and experimentations are presented to validate this simple, original and efficient modulation concept equivalent to matrix converter SVM.; TRavaux de thèses financé par le pole MEDEE, La région Nord pas de calais et STIE (Schneider Toshiba Inverter Europe)

Melhorias na disciplina de custos identificadas por meio da utilização conjunta do modelo kano de qualidade e da matriz de importância e desempenho; Improvement in the subject of costs using the kano model of quality and the matrix of importance and performance

Cunha, Paulo Roberto da; Klann, Roberto Carlos; Silva, Júlio Orestes da; Scarpin, Jorge Eduardo
Fonte: Universidade de São Paulo. Faculdade de Economia, Administração e Contabilidade de RP Publicador: Universidade de São Paulo. Faculdade de Economia, Administração e Contabilidade de RP
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; ; Formato: application/pdf
Publicado em 01/08/2010 POR
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O objetivo desta pesquisa foi aplicar a técnica do modelo Kano de Qualidade Atrativa e Obrigatória em conjunto com a Matriz de Importância e Desempenho para identificar oportunidades de melhoria na disciplina de custos de diferentes cursos de graduação. O delineamento metodológico caracteriza-se por um estudo descritivo, por um levantamento com uma abordagem quantitativa e por uma etapa prévia qualitativa . A população da pesquisa foi definida de forma intencional, em linha com o objeto de estudo, em que os sujeitos foram os alunos que cursam a disciplina de custos nos cursos de administração, ciências contábeis, ciências econômicas, engenharia de produção e moda de uma universidade do Sul do país, perfazendo o total de 289 alunos. A amostra por acessibilidade foi de 214 alunos, ou seja, 74%. O instrumento utilizado para coleta de dados foi um questionário com base no modelo Kano de qualidade atrativa e obrigatória adaptado de Walter, Tontini e Domingues (2005), complementado por atributos identificados por meio da aplicação da técnica de focus group. O instrumento contemplou a possibilidade de análise de 23 atributos, agrupados em cinco categorias: capacitação dos professores, métodos de ensino, atitude...

The effect of the matrix structure on the metal dusting rate in hydrocarbon environments

Slabbert,G.A.; Mulaudzi,F.M.L.; Cornish,L.A.; Papo,M.J.; Morudu,V.; Zhang,J.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2013 EN
Relevância na Pesquisa
65.45%
The paper describes work undertaken to identify the influence of the matrix structure on the metal dusting rate of stainless steel alloys. Specifically, the difference in metal dusting rate between austenitic and ferritic stainless steels of similar chromium contents was investigated. The alloys were exposed to metal dusting conditions and their performance compared by weight loss, optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The specific gas mixture used for all the tests were 18.9% CO-79.1% H2-2% H2O at 650°C. For austenitic stainless steels, Types 304, 321, 316, and 316Ti were compared to two ferritic grades, namely Types 430 and 441. The resistance of the ferritic grades was found to be significantly better than that of the austenitic grades. This was attributed to greater permeability of chromium through the matrix structure to maintain the protective oxide scale. The results will be used in the development of novel alloys to combat metal dusting.