Determinação das curvas de carga do polipropileno deformado via técnica de prensagem em canais equiangulares / Determination of polypropylene load curves by equal channel angular pressing technique

 O objetivo deste estudo é determinar as curvas de carga do polímero termoplástico polipropileno deformado a partir da técnica de prensagem em canais equiangulares, PCEA, através de diferentes rotas de processamento e temperaturas de ensaio. Foram realizados quatro passes de deformação considerando-se as rotas A e B, que são determinadas de acordo com o sentido de rotação da amostra entre os passes de prensagem durante os ensaios, sendo que na rota A as amostras não sofrem rotação e na rota B, a partir de BA e BC, há rotações de 90º alternadas para BA e no mesmo sentido para BC. Ainda, as temperaturas de 25 °C e 90 °C, sendo esta última correspondente a 50% da temperatura de fusão do polipropileno, foram consideradas para os testes via PCEA. Os resultados mostraram que as deformações aplicadas sofreram influência da temperatura de processamento e a rota A obteve os maiores valores de carga máxima em relação às rotas BA e BC a 25 ºC apresentando amostras com maiores distorções.

Determinação das curvas de carga do polipropileno deformado via técnica de prensagem em canais equiangulares / Determination of polypropylene load curves by equal channel angular pressing technique

 O objetivo deste estudo é determinar as curvas de carga do polímero termoplástico polipropileno deformado a partir da técnica de prensagem em canais equiangulares, PCEA, através de diferentes rotas de processamento e temperaturas de ensaio. Foram realizados quatro passes de deformação considerando-se as rotas A e B, que são determinadas de acordo com o sentido de rotação da amostra entre os passes de prensagem durante os ensaios, sendo que na rota A as amostras não sofrem rotação e na rota B, a partir de BA e BC, há rotações de 90º alternadas para BA e no mesmo sentido para BC. Ainda, as temperaturas de 25 °C e 90 °C, sendo esta última correspondente a 50% da temperatura de fusão do polipropileno, foram consideradas para os testes via PCEA. Os resultados mostraram que as deformações aplicadas sofreram influência da temperatura de processamento e a rota A obteve os maiores valores de carga máxima em relação às rotas BA e BC a 25 ºC apresentando amostras com maiores distorções.

Influence of ECAPressing temperature on crystallinity and mechanical behaviour of polypropylene and high-density polyethylene / Influência da temperatura de ECAPressing na cristalinidade e comportamento mecânico do polipropileno e do polietileno de alta densidade

In this paper, the influence of single equal channel angular pressing, ECAPressing, pass and processing temperature on crystallinity evolution and mechanical behaviour of the polymers polypropylene, PP, and high-density polyethylene, HDPE was investigated. ECAPressing tests were performed at the temperatures of 25, 50, 75 and 100°C for HPDE and 25, 90 and 120ºC for PP. The materials mechanical behaviour before and after ECAPressing tests was evaluated from room temperature compression tests while their crystallinity changings were analyzed through differential scanning calorimetry, DSC, experiments. In terms of strengthening and by comparison with as-received materials, it was observed an interesting efficiency of ECAPressing performed at 100°C for HDPE and 120°C for PP. In relation to crystallinity evolution, the results obtained from DSC tests showed its considerable increasing for higher pressing temperatures also by comparing either to as-received conditions or after single pass of equal channel angular pressing at room temperature

Nonabelian (2,0) Tensor Multiplets and 3-algebras

Using 3-algebras we obtain a nonabelian system of equations that furnish a representation of the (2,0)-supersymmetric tensor multiplet. The on-shell conditions are quite restrictive so that the system can be reduced to five-dimensional gauge theory along with six-dimensional abelian (2,0) tensor multiplets. We briefly discuss possible applications to D4-branes using a spacelike reduction and M5-branes using a null reduction.Comment: 17 pages, Latex; v2: Typos corrected and references adde

Análise da ocorrência de desgaste por fretting em varetas combustíveis nucleares de Zr-1Nb-Sn-0.1Fe / Analysis of fretting wear occurrence on Zr-1Nb-1Sn-0.1Fe nuclear fuel rods

Estudos mostraram que o fretting, uma espécie de atrito acelerado por vibração devido ao fluxo de refrigerante, é a principal causa de falhas das varetas dos elementos combustíveis. No presente trabalho estudou-se o comportamento de varetas combustíveis fabricados a partir da liga Zr-1Nb-1Sn-0,1Fe, submetidas a ensaios físicos que visam reproduzir a ocorrência de fretting. Para isso, pretende-se realizar análises microestrutural via microscopia óptica (MO) e eletrônica de varredura (MEV) e testes de desgaste sobre tal liga nas condições como recebido em diferentes posições da grade espaçadora. Os ensaios físicos para a ocorrência de fretting foram realizados através de um protótipo disponível no laboratório de Conformação e Tratamentos Termomecânicos da EEIMVR/UFF. Esse equipamento foi operado na frequência de 30 Hz por períodos de 24 horas, induzindo deslocamentos horizontais aos tubos em relação à grade espaçadora também fabricada a partir da liga Zr-1Nb-1Sn-0,1Fe. As regiões externas da grade foram aquelas que apresentaram maior desgaste devido a rigidez imposta ao sistema nessas regiões. As imagens das regiões afetadas mostraram que o relevo apresentou regiões de crateras e picos ocasionados por arrancamento de material. Além disso, nas regiões desbastadas sem arrancamento, ficou claro que há início de propagação de trincas, que ao longo do tempo levará a fraturas por arrancamento.

On the mechanical behavior of an Al 7075 alloy deformed by asymmetrical and conventional rolling

Samples of the Al 7075 naturally and artificially aged were processed by conventional and asymmetricalrolling with 5% of thickness reduction. The rolling processes were evaluated under room temperature andunder warm condition (130°C). Mechanical properties were evaluated by uniaxial tensile and Vickersmicrohardness tests. Microstructure evolutions were followed by optical microscopy analysis. Naturally agedsamples showed better yield strengthening under warm processing. Greater ultimate stress and ductility underroom temperature processing was also noticed in naturally aged specimens. Artificially aged samples showedbetter mechanical properties under room temperature, softening under warm processing due to grain recoveryprocess. Microhardness tests showed expected results for both rolling types, especially on asymmetricalrolling with the higher predictions were observed. Micrographs have shown no expressive grain changes orrefinement although its flattening was observed. Precipitates were analyzed by EDS/SEM revealing thepresence of MgZn2 and CuMgAl along the matrix that provides plastic strengthening.Keywords: Aging, asymmetrical rolling, conventional rolling, mechanical behavior, Al 7075 alloy

Detecting Endometrial Cancer by Blood Spectroscopy: A Diagnostic Cross-Sectional Study

Endometrial cancer is the sixth most common cancer in women, with a rising incidence worldwide. Current approaches for the diagnosis and screening of endometrial cancer are invasive, expensive or of moderate diagnostic accuracy, limiting their clinical utility. There is a need for cost-effective and minimally invasive approaches to facilitate the early detection and timely management of endometrial cancer. We analysed blood plasma samples in a cross-sectional diagnostic accuracy study of women with endometrial cancer (n = 342), its precursor lesion atypical hyperplasia (n = 68) and healthy controls (n = 242, total n = 652) using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and machine learning algorithms. We show that blood-based infrared spectroscopy has the potential to detect endometrial cancer with 87% sensitivity and 78% specificity. Its accuracy is highest for Type I endometrial cancer, the most common subtype, and for atypical hyperplasia, with sensitivities of 91% and 100%, and specificities of 81% and 88%, respectively. Our large-cohort study shows that a simple blood test could enable the early detection of endometrial cancer of all stages in symptomatic women and provide the basis of a screening tool in high-risk groups. Such a test has the potential not only to differentially diagnose endometrial cancer but also to detect its precursor lesion atypical hyperplasia—the early recognition of which may allow fertility sparing management and cancer prevention

Monitoring the Morphology of M87* in 2009–2017 with the Event Horizon Telescope

The Event Horizon Telescope (EHT) has recently delivered the first resolved images of M87*, the supermassive black hole in the center of the M87 galaxy. These images were produced using 230 GHz observations performed in 2017 April. Additional observations are required to investigate the persistence of the primary image feature—a ring with azimuthal brightness asymmetry—and to quantify the image variability on event horizon scales. To address this need, we analyze M87* data collected with prototype EHT arrays in 2009, 2011, 2012, and 2013. While these observations do not contain enough information to produce images, they are sufficient to constrain simple geometric models. We develop a modeling approach based on the framework utilized for the 2017 EHT data analysis and validate our procedures using synthetic data. Applying the same approach to the observational data sets, we find the M87* morphology in 2009–2017 to be consistent with a persistent asymmetric ring of ~40 μas diameter. The position angle of the peak intensity varies in time. In particular, we find a significant difference between the position angle measured in 2013 and 2017. These variations are in broad agreement with predictions of a subset of general relativistic magnetohydrodynamic simulations. We show that quantifying the variability across multiple observational epochs has the potential to constrain the physical properties of the source, such as the accretion state or the black hole spin