71 results on '"Santiago Coelho"'
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2. Determinants of the spread of vehicle electrification and directions for the brazilian market
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Flavio Garcia de Oliveira Soares Filho, Paulo Soares Figueiredo, Rodrigo Santiago Coelho, Lis Lisboa Bernardino, and Xisto Lucas Travassos Junior
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- 2023
3. BIBLIOMETRIC ANALYSIS FOR SIMULATING THE BEHAVIOR OF ADHESIVES USING THE MESHLESS METHOD
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Petrucio Leal Pereira, Valter Estevão Beal, Juan Carlos Romero Albino, Jade Spinola Avila, and Rodrigo Santiago Coelho
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- 2022
4. A QUICK LOOK INTO THE ADDITIVE MANUFACTURING IN BRAZIL: FIRST IMPRESSIONS
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Joyce Mara Brito Maia, Bruno Caetano dos Santos Silva, and Rodrigo Santiago Coelho
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- 2022
5. Exact solution of a time-dependent quantum harmonic oscillator with two frequency jumps via the Lewis-Riesenfeld dynamical invariant method
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Danilo T. Alves, Stanley Santiago Coelho, and Lucas Queiroz
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Quantum Physics ,FOS: Physical sciences ,General Physics and Astronomy ,Lewis–Riesenfeld method ,quantum harmonic oscillator ,abrupt jumps ,Quantum Physics (quant-ph) - Abstract
Harmonic oscillators with multiple abrupt jumps in their frequencies have been investigated by several authors during the last decades. We investigate the dynamics of a quantum harmonic oscillator with initial frequency $\omega_0$, that undergoes a sudden jump to a frequency $\omega_1$ and, after a certain time interval, suddenly returns to its initial frequency. Using the Lewis-Riesenfeld method of dynamical invariants, we present expressions for the mean energy value, the mean number of excitations, and the transition probabilities, considering the initial state different from the fundamental. We show that the mean energy of the oscillator, after the jumps, is equal or greater than the one before the jumps, even when $\omega_1, Comment: 11 pages, 12 figures
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- 2022
6. Evaluation of the Friction Coefficient for TRIP1000 Steel under Different Conditions of Lubrication, Contact Pressure, Sliding Speed and Working Temperature
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Luis Fernando Folle, Bruno Caetano dos Santos Silva, Marcelo Sousa de Carvalho, Luiz Gustavo Souza Zamorano, and Rodrigo Santiago Coelho
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friction coefficient ,pin-on-disk test ,high strength steels ,TRIP1000 ,sheet metal forming ,lubrication ,contact pressure ,sliding speed ,working temperature ,Metals and Alloys ,General Materials Science - Abstract
The use of ultra-high-strength steels (UHSS) has been growing in recent years, mainly in the automotive industry. Since these steels have high strength and hardness, more applied stresses are required to deform them, probably also impacting friction behaviour. In this article, a variation in the process parameters commonly observed in sheet-metal forming, such as contact pressure, sliding speed, lubrication and working temperature was performed. The material used was TRIP1000. These process parameters were varied, aiming to investigate the friction-coefficient behaviour; however, it was observed that there were no significant variations, indicating that the steel hardness may have contributed to this. Another finding is that, even if the lubricant did not change the average value of the friction coefficient, it contributed to a more stable process, favouring the absence of premature wear of the tools.
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- 2022
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7. PERTURBAÇÕES DA APRENDIZAGEM: ATRASO E DIFICULDADES NO DESENVOLVIMENTO ESCOLAR DA CRIANÇA
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Mislane Santiago Coelho, Ana Paula Leite Cardiliquio, Hemerson Milani Mendes, Jaqueline Custódio Chagas Soares, Vilene Costa Santos Bedelegue, and Julia Cristina Feitoza Mota
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- 2022
8. The Role of Friction on Metal Forming Processes
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Luis Fernando Folle, Bruno Caetano dos Santos Silva, Gilmar Ferreira Batalha, and Rodrigo Santiago Coelho
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The friction that occurs in forming processes plays a fundamental role in the industry as it can be responsible for both manufacturing failure and its success. Scientific research has been done to try to understand this phenomenon as well as simulation software has been implemented aiming to predict the tribological behavior of the metallic pair in contact. Thus, this chapter is dedicated to the analysis of the main parameters that can influence the coefficient of friction, especially for metal manufacturing processes. Some simulation models that try to predict the behavior of friction under certain conditions of process speed, contact pressure and operating temperature will also be presented.
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- 2022
9. New aspects of globularization crystallography and dynamic phase evolution during thermomechanical processing of Ti���6Al���4V alloy
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Rodrigo Santiago Coelho, Bruna Callegari, Pedro Paiva Brito, Haroldo Cavalcanti Pinto, Flavio Soldera, Frank Mücklich, João Pedro Oliveira, and Norbert Schell
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Shearing (physics) ,MATERIAIS ,Materials science ,Misorientation ,Strain rate ,Condensed Matter Physics ,Condensed Matter::Materials Science ,Crystallography ,Dynamic recrystallization ,Thermomechanical processing ,ddc:530 ,General Materials Science ,Texture (crystalline) ,Deformation (engineering) ,Electron backscatter diffraction - Abstract
Materials chemistry and physics 276, 125388 (2022). doi:10.1016/j.matchemphys.2021.125388, Microstructural and crystallographic aspects arising from thermomechanical processing of a Ti���6Al���4V alloy in ��and ��+�� phase fields were studied by electron backscatter diffraction and both conventional and high energysynchrotron X-ray diffraction. The impact of deformation in the single �� field on the final microstructure has beenacknowledged by an increase of the retained �� phase content and decrease of martensitic c/a ratio with thereduction of strain rate, although no significant influence of strain rate on the well-defined fiber texture of ����� hasbeen observed. During deformation in the ��+�� field, texture weakening has been observed, and misorientationangle/axis distribution analysis has evidenced randomization and loss of the Burgers orientation relationshipbetween �� and �� upon globularization. The behavior of deformed �� lamellae in the ��+�� field was also evaluatedin terms of internal misorientation spread and lattice rotation around the deformation axis, corroborating thatglobularization takes place through dynamic recrystallization, boundary splitting and shearing. Globularizedgrain size was shown to be exponentially proportional to strain rate decrease. Lower strain rates in the ��+�� fieldalso increase the �� phase fraction and decrease the c/a ratio of the �� phase, leading to values closer to the idealone for titanium. However, an excessive amount of �� causes its instability during quenching, resulting in itsdecomposition into secondary �� during cooling., Published by Elsevier, New York, NY [u.a.]
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- 2022
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10. O ESPAÇO DA EMOÇÃO E SUA IMPORTÂNCIA NO PROCESSO DE COMUNICAÇÃO, RELAÇÃO INTERPESSOAL, APRENDIZAGEM E A NEUROCIÊNCIA NESSA CONJUNTURA
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Mislane Santiago Coelho, Ana Paula Leite Cardiliquio, Maria Creuza de Souza, Hemerson Milani Mendes, and Alanna Severino Duarte Silva
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- 2021
11. TRANSTORNO DO ESPECTRO DO AUTISMO (TEA) E A APRENDIZAGEM DA MATEMÁTICA
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Maria Madalena Leite da Costa, Mislane Santiago Coelho, Ana Paula Leite Cardiliquio, Hemerson Milani Mendes, and Julia Cristina Feitoza Mota
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- 2021
12. Population‐based Bayesian regularization for microstructural diffusion MRI with NODDIDA
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Meghdoot Mozumder, Alejandro F. Frangi, Jose M. Pozo, and Santiago Coelho
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Adult ,microstructure imaging ,Computer science ,Bayesian probability ,Population ,030218 nuclear medicine & medical imaging ,Full Papers—Computer Processing and Modeling ,diffusion MRI ,03 medical and health sciences ,0302 clinical medicine ,Robustness (computer science) ,biophysical tissue models ,Prior probability ,Image Processing, Computer-Assisted ,Neurites ,Maximum a posteriori estimation ,Humans ,Radiology, Nuclear Medicine and imaging ,education ,education.field_of_study ,Bayes estimator ,Human Connectome Project ,Full Paper ,Estimation theory ,business.industry ,Brain ,modeling ,Bayes Theorem ,Pattern recognition ,Middle Aged ,3. Good health ,Diffusion Magnetic Resonance Imaging ,Artificial intelligence ,parameter estimation ,business ,030217 neurology & neurosurgery - Abstract
Purpose Information on the brain microstructure can be probed by Diffusion Magnetic Resonance Imaging (dMRI). Neurite Orientation Dispersion and Density Imaging with Diffusivities Assessment (NODDIDA) is one of the simplest microstructural model proposed. However, the estimation of the NODDIDA parameters from clinically plausible dMRI acquisition is ill‐posed, and different parameter sets can describe the same measurements equally well. A few approaches to resolve this problem focused on developing better optimization strategies for this non‐convex optimization. However, this fundamentally does not resolve ill‐posedness. This article introduces a Bayesian estimation framework, which is regularized through knowledge from an extensive dMRI measurement set on a population of healthy adults (henceforth population‐based prior). Methods We reformulate the problem as a Bayesian maximum a posteriori estimation, which includes as a special case previous approach using non‐informative uniform priors. A population‐based prior is estimated from 35 subjects of the MGH Adult Diffusion data (Human Connectome Project), acquired with an extensive acquisition protocol including high b‐values. The accuracy and robustness of different approaches with and without the population‐based prior is tested on subsets of the MGH dataset, and an independent dataset from a clinically comparable scanner, with only clinically plausible dMRI measurements. Results The population‐based prior produced substantially more accurate and robust parameter estimates, compared to the conventional uniform priors, for clinically feasible protocols, without introducing any evident bias. Conclusions The use of the proposed Bayesian population‐based prior can lead to clinically feasible and robust estimation of NODDIDA parameters without changing the acquisition protocol.
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- 2019
13. Adding Technology Sustainability Evaluation to Product Development: A Proposed Methodology and an Assessment Model
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Bruna Aparecida Souza Machado, André Souza Oliveira, Bruno Caetano dos Santos Silva, Rodrigo Santiago Coelho, Cristiano Vasconcellos Ferreira, and Renelson Ribeiro Sampaio
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0209 industrial biotechnology ,Computer science ,Emerging technologies ,020209 energy ,Geography, Planning and Development ,TJ807-830 ,Context (language use) ,02 engineering and technology ,Management, Monitoring, Policy and Law ,TD194-195 ,product-development processes ,Renewable energy sources ,Strategy development ,020901 industrial engineering & automation ,0202 electrical engineering, electronic engineering, information engineering ,GE1-350 ,Life Cycle Engineering ,Environmental effects of industries and plants ,Renewable Energy, Sustainability and the Environment ,business.industry ,decision-making ,sustainability ,technology maturity ,Variety (cybernetics) ,Environmental sciences ,Sustainable products ,Risk analysis (engineering) ,Life Cycle Engineering (LCE) ,Sustainability ,New product development ,business - Abstract
In the current world scenario, which is experiencing the arrival of new technologies, Industry 4.0, increased mobility and a pandemic environment, the achievement of sustainability demands proactive solutions. One of these actions includes the design of sustainable products. Several authors have studied the scientific discipline of Life Cycle Engineering (LCE), which encompasses environmental, social and economic dimensions. However, current LCE models have gaps, such as the need to incorporate a more holistic view, uncertainty and integrated analysis. In this context, the aim of this paper is to present a model to evaluate the technology sustainability (TS) dimension. The methodology of the present work involves a literature review, the development of a model with qualitative and quantitative data, and application in a case study. A structure was developed to include market, technical, and technology-scaling perspectives. The computational model uses hybrid Bayesian networks, based on probabilistic theory, and incorporates uncertainty using sustainability indicators. The model includes quantitative and qualitative variables derived from experts’ opinions. The results of applying the model to a real research project on manhole covers indicate that this analytical tool can support decision-making, allowing a new dimension to be incorporated into LCE analysis. Finally, the model allows LCE analysis to be applied in a variety of circumstances, such as strategy development or the selection of more sustainable products, as well as the evaluation of competing products.
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- 2021
14. Tissue microarray (TMA) use in post mortem neuropathology
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L A Wilson, Santiago Coelho, J R Highley, B A Ashford, Paul G. Ince, L Heraty, Jose M. Pozo, and Alejandro F. Frangi
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0301 basic medicine ,Pathology ,medicine.medical_specialty ,Tissue microarray ,business.industry ,General Neuroscience ,Neuropathology ,Grey matter ,Immunohistochemistry ,Sensitivity and Specificity ,Hyperintensity ,Volume density ,White matter ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,medicine.anatomical_structure ,Tissue Array Analysis ,medicine ,Microglial cell ,business ,030217 neurology & neurosurgery - Abstract
Background\ud \ud Tissue microarrays (TMAs), where each block (and thus section) contains multiple tissue cores from multiple blocks potentially allow more efficient use of tissue, reagents and time in neuropathology.\ud \ud \ud \ud New Method\ud \ud The relationship between data from TMA cores and whole sections was investigated using ‘virtual’ TMA cores. This involved quantitative assessments of microglial pathology in white matter lesions and motor neuron disease, alongside qualitative TDP-43 inclusion status in motor neuron disease cases. Following this, a protocol was developed for TMA construction.\ud \ud \ud \ud Results\ud \ud For microglial pathology we found good concordance between virtual cores and whole sections for volume density using one 1.75 mm core (equivalent to a 2 mm core after accounting for peripheral tissue loss). More sophisticated microglial cell size and measures required two cores. Qualitative results of pTDP-43 pathology showed use of one 1.75 mm core gave a 100% sensitivity and specificity within grey matter, and 88.3% sensitivity and 100% specificity within white matter. A method of producing the TMAs was suitable for immunohistochemistry both manually and by autostainer, with the minimal core loss from the microscope slide.\ud \ud \ud \ud Comparison with Existing Methods\ud \ud TMAs have been used infrequently in post mortem neuropathology research. However, we believe TMAs give comparable tissue assessment results and can be constructed, sectioned and stained with relative ease.\ud \ud \ud \ud Conclusions\ud \ud We found TMAs could be used to assess both quantitative (microglial pathology) and qualitative pathology (TDP-43 proteinopathy) with greatly reduced quantities of tissue, time and reagents. These could be used for further work to improve data acquisition efficiency.
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- 2021
15. Método de tomada de decisão visando produtos sustentáveis
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Rodrigo Santiago Coelho, André Souza Oliveira, Luiz Miguel Sergani Costa, Paulo Henrique Ferreira, Enrique López Droguett, Renelson Ribeiro Sampaio, and Cristiano Vasconcellos Ferreira
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- 2021
16. METHODS ANALYSIS FOR PHASE MEASUREMENT IN WELDED SAMPLE OF SUPERDUPLEX STAINLESS STEEL UNS S32750
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Francisco Magalhães dos Santos Júnior, Tiago Nunes Lima, Rodrigo Santiago Coelho, Bruno Caetano dos Santos Silva, Leonardo Oliveira Passos da Silvaa, Alexandre Ferraz Dourado, Daniel Marques de Souza, and Luã Fonseca Seixas
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Materials science ,law ,Phase (matter) ,Metallurgy ,Welding ,Sample (graphics) ,law.invention - Published
- 2020
17. A NEW AND EFFECTIVE DECISION-MAKING PLATFORM FOR BATTERY SELECTION AIMING TO ACHIEVE STANDARDIZATION IN MINING INDUSTRY
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Lílian Lefol Nani Guarieiro, Estevão Gomes, Alexandre Alves da Silva, César Catizane, Rodrigo Santiago Coelho, and Edmundo Neto
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Battery (electricity) ,Mining industry ,Standardization ,Computer science ,Manufacturing engineering ,Selection (genetic algorithm) - Published
- 2020
18. Tribological Investigations on Tool Surfaces for Temperature-Supported Forming of Magnesium AZ31 Sheets
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Alisson Mendes Rodrigues, Haroldo Cavalcanti Pinto, Fábio André Lora, Bruno Caetano dos Santos Silva, Marcio Luis Ferreira Nascimento, Rodrigo Santiago Coelho, Roland Mueller, and Publica
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Surface (mathematics) ,Materials science ,chemistry.chemical_element ,02 engineering and technology ,lcsh:Technology ,Article ,0203 mechanical engineering ,LIGAS METÁLICAS ,tool design ,friction coefficient ,General Materials Science ,Composite material ,Magnesium alloy ,lcsh:Microscopy ,forming process ,lcsh:QC120-168.85 ,Friction coefficient ,periodic surface structures ,lcsh:QH201-278.5 ,Magnesium ,lcsh:T ,Forming processes ,magnesium alloy AZ31 ,Tribology ,021001 nanoscience & nanotechnology ,Tool design ,020303 mechanical engineering & transports ,chemistry ,lcsh:TA1-2040 ,lcsh:Descriptive and experimental mechanics ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,0210 nano-technology ,lcsh:Engineering (General). Civil engineering (General) ,lcsh:TK1-9971 - Abstract
Aiming to decrease friction coefficient () during the forming of magnesium alloy sheets, nine (9) tools with different hole geometries in their surface (flat, elliptical, and circular) were manufactured from steel Boehler W400 VMR (as known as DIN 1.2343).. Tribological investigations were accomplished on a strip drawing machine at 288 °, C without lubricants. When compared with a standard tool (surface flat), on average, tools with circular geometries in their surface showed the smallest friction coefficient, while tools with elliptical geometries shown higher. The friction coefficient also was confronted with the ratio between area occupied by holes in the surface of the tool and the total tool surface (i.e., factor f (%)), hole diameter (Ø, ), and the distance between circle centers (d(c,c)). Principal Component Analysis (PCA) complemented the experimental approach. In summary, both approaches (experimental and theoretical) indicated that the manufactured tool with circular geometries on its surface presented lower friction coefficient values on the forming processes of the magnesium AZ31 sheets.
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- 2020
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19. In-situ synchrotron radiation study of the aging response of Ti-6Al-4V alloy with different starting microstructures
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João Pedro Oliveira, Pedro Paiva Brito, Katherine Aristizabal, F. Mücklich, L. Wu, Flavio Soldera, N. Schell, Haroldo Cavalcanti Pinto, Rodrigo Santiago Coelho, and Bruna Callegari
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Materials science ,Alloy ,Intermetallic ,02 engineering and technology ,engineering.material ,01 natural sciences ,law.invention ,law ,ddc:670 ,0103 physical sciences ,General Materials Science ,Lamellar structure ,DIFRAÇÃO POR RAIOS X ,010302 applied physics ,Mechanical Engineering ,Titanium alloy ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,Synchrotron ,Chemical engineering ,Mechanics of Materials ,Martensite ,engineering ,Hardening (metallurgy) ,0210 nano-technology - Abstract
Materials characterization 165(110400), 1-10 (2020). doi:10.1016/j.matchar.2020.110400, The aging behavior of a Ti-6Al-4V alloy with different starting microstructures was evaluated by means ofsynchrotron X-ray diffraction, scanning-transmission electron microscopy and micro-hardness measurements.Initial microstructures were produced by thermal and thermomechanical treatments and comprised differentmorphologies of �� phase (martensitic, lamellar, bimodal and globular), as well as the presence or absence of the�� phase. Results show that one or more of the following phenomena can take place during aging and contributeto the hardening of the alloy: �� decomposition into fine secondary �� laths; transformation of the metastablemartensitic ����� into the equilibrium �� phase; and precipitation of the intermetallic Ti$_3$Al. The composition anddistribution of the �� phase was shown to affect the precipitation of secondary �� during aging, while the compositionof the �� phase plays a key role on the formation of Ti$_3$Al. In situ X-ray diffraction studies of the earlystages of aging show the kinetics of the ���������� conversion by the reduction in FWHM of XRD reflections, indicatethe contribution to hardening by the increase of the c/a ratio and the consequent limitation of active slip systemsand depict the chemical homogenization and decomposition of the �� phase., Published by Science Direct, New York, NY
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- 2020
20. In situ evaluation of the low-temperature aging response of Ti–5Al–5Mo–5V–3Cr alloy as influenced by starting microstructure
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Rodrigo Santiago Coelho, Flavio Soldera, Sebastian Suarez, Pedro Paiva Brito, Bruna Callegari, Haroldo Cavalcanti Pinto, Katherine Aristizabal, L. Wu, José Garcia, and F. Mücklich
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In situ ,Materials science ,MATERIAIS ,Precipitation (chemistry) ,Mechanical Engineering ,Alloy ,Metals and Alloys ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Synchrotron ,Isothermal process ,0104 chemical sciences ,law.invention ,Chemical engineering ,Mechanics of Materials ,law ,Phase (matter) ,Materials Chemistry ,engineering ,Deformation (engineering) ,0210 nano-technology - Abstract
The impact of starting microstructure on the isothermal behavior of β-metastable Ti–5Al–5Mo–5V–3Cr alloy during aging at 400 °C for 8 h was studied by means of in situ synchrotron X-ray diffraction. Results show that prior deformation does not accelerate phase precipitation during heating, but has an influence on secondary α precipitation during aging, and that the composition of the β matrix, which is affected by the amount of primary α formed depending on the preliminary processing route applied, plays a major role. At this aging temperature, α" phase tends to form from the β matrix in high quantities without the presence of primary α phase or with a low fraction of this phase, and the conversion of α" into α is sluggish, being faster in the β-heat-treated condition, whereas a continuous β → α transformation occurs, with no reliable evidence of α" precipitation, in the α+β-heat-treated condition. Isothermal precipitation was enough to promote a significant hardness increase in the alloy. Observation of the behavior of α" based on its atomic y-coordinate and orthorhombicity helped to elucidate its transformation pathway.
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- 2020
21. On manufacturing multilayer-like nanostructures using misorientation gradients in PVD films
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Flavio Soldera, Rodrigo Santiago Coelho, Fabiola Pineda, Haroldo Cavalcanti Pinto, José Garcia, Pedro Renato Tavares Avila, Alisson Mendes Rodrigues, Katherine Aristizabal, Magdalena Walczak, and Erenilton Pereira da Silva
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Multidisciplinary ,Materials science ,Misorientation ,Synthesis and processing ,lcsh:R ,lcsh:Medicine ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,Article ,Surfaces, interfaces and thin films ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Residual stress ,Physical vapor deposition ,Surface roughness ,lcsh:Q ,TRIBOLOGIA ,Grain boundary ,Texture (crystalline) ,Composite material ,High-power impulse magnetron sputtering ,lcsh:Science ,0210 nano-technology - Abstract
Due to their applicability for manufacturing dense, hard and stable coatings, Physical Vapor Deposition (PVD) techniques, such as High Power Impulse Magnetron Sputtering (HiPIMS), are currently used to deposit transition metal nitrides for tribological applications. Cr-Al-N is one of the most promising ceramic coating systems owing to its remarkable mechanical and tribological properties along with excellent corrosion resistance and high-temperature stability. This work explores the possibility of further improving Cr-Al-N coatings by modulation of its microstructure. Multilayer-like Cr1−xAlxN single films were manufactured using the angular oscillation of the substrate surface during HiPIMS. The sputtering process was accomplished using pulse frequencies ranging from 200 to 500 Hz and the resulting films were evaluated with respect to their hardness, Young’s modulus, residual stresses, deposition rate, crystallite size, crystallographic texture, coating morphology, chemical composition, and surface roughness. The multilayer-like structure, with periodicities ranging from 250 to 550 nm, were found associated with misorientation gradients and small-angle grain boundaries along the columnar grains, rather than mesoscopic chemical modulation of the microstructure. This minute modification of microstructure along with associated compressive residual stresses are concluded to explain the increased hardness ranging from 25 to 30 GPa, which is at least 20% over that expected for a film of the same chemical composition grown by a conventional PVD processing route.
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- 2019
22. OS DESAFIOS DA USINAGEM DE AÇOS INOXIDÁVEIS AUSTENÍTICOS: UMA BREVE INTRODUÇÃO
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Francisco Magalhães dos Santos Júnior, Leonardo Oliveira Passos da Silva, Guilherme Oliveira de Souza, Advan Coelho Nascimento, and Rodrigo Santiago Coelho
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- 2019
23. SIMULAÇÃO NUMÉRICA E FÍSICA NA SOLDAGEM DOS AÇOS INOXIDÁVEIS DUPLEX: UMA REVISÃO SISTEMÁTICA
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Advan Coelho Nascimento, Rodrigo Santiago Coelho, Bruno Caetano dos Santos Silva, Tiago Nunes Lima, Leonardo Oliveira Passos da Silva, and Francisco Magalhães dos Santos Júnior
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- 2019
24. ESTUDO INTRODUTÓRIO DA SOLDABILIDADE DO AÇO 22MnB5 PELO PROCESSO DE SOLDAGEM A PONTO POR RESISTÊNCIA
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Francisco Magalhães dos Santos Júnior, Leonardo Oliveira Passos da Silva, Advan Coelho Nascimento, and Rodrigo Santiago Coelho
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- 2019
25. Estimation of residual stresses in perovskite films for capacitor applications
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David Horwat, Sebastian Slawik, F. Mücklich, Björn Lechthaler, Sylvie Migot, P. Leibenguth, Rodrigo Santiago Coelho, and E. Ramos-Moore
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010302 applied physics ,Fabrication ,Materials science ,Metals and Alloys ,02 engineering and technology ,Surfaces and Interfaces ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Stress (mechanics) ,Residual stress ,Phase (matter) ,0103 physical sciences ,Electrode ,Materials Chemistry ,Deposition (phase transition) ,Composite material ,0210 nano-technology ,Perovskite (structure) - Abstract
The performance of perovskite films in capacitor devices is strongly determined by the level of residual stresses developed after their fabrication at high temperatures. Quantification of these stresses by X-ray diffraction is not straightforward in perovskite films due to the complexity of the crystalline structure and a lack of effective elastic diffraction constants. In this work we apply a simple and accurate method to estimate the residual stresses developed in Pb(Nb,Zr,Ti)O3 perovskite films grown by metal–organic chemical vapor deposition on the Pt electrode. The stress was directly measured in the Pt bottom electrode film before and after the deposition of the perovskite film and compared with intrinsic and thermal stresses calculations. Our results reveal in-plane tensile stresses of 676(8) MPa developed in the Pt electrode, which mainly originate from the relative thermal contraction between Pb(Nb,Zr,Ti)O3 and Pt as well as the cubic-tetragonal perovskite phase transformation after deposition. This methodology is straightforward and highlights the possibility to perform systematic studying for tailoring stress conditions and improving the performance of perovskite films for capacitor applications.
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- 2018
26. Collaborative and Structured Network for Maintenance of Mechanical Ventilators during the SARS-CoV-2 Pandemic
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Bruno Caetano dos Santos Silva, Bruna Aparecida Souza Machado, Daniel Motta, Rodrigo Santiago Coelho, Luiz Fernando Taboada Gomes Amaral, Willams Teles Barbosa, and Lucas de Freitas Gomes
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Leadership and Management ,Collaborative network ,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ,Medical equipment ,Health Informatics ,Article ,maintenance ,03 medical and health sciences ,0302 clinical medicine ,Health Information Management ,Pandemic ,Health care ,medicine ,030212 general & internal medicine ,030304 developmental biology ,0303 health sciences ,SARS-CoV-2 ,business.industry ,pandemic ,Health Policy ,mechanical pulmonary ventilators ,collaborative network ,medicine.disease ,Work (electrical) ,Software deployment ,Medicine ,Private healthcare ,Medical emergency ,business - Abstract
The SARS-CoV-2 pandemic in Brazil has grown rapidly since the first case was reported on 26 February 2020. As the pandemic has spread, the low availability of medical equipment has increased, especially mechanical ventilators. The Brazilian Unified Health System (SUS) claimed to have only 40,508 mechanical ventilators, which would be insufficient to support the Brazilian population at the pandemic peak. This lack of ventilators, especially in public hospitals, required quick, assertive, and effective actions to minimize the health crisis. This work provides an overview of the rapid deployment of a network for maintaining disused mechanical ventilators in public and private healthcare units in some regions of Brazil during the SARS-CoV-2 pandemic. Data referring to the processes of maintaining equipment, acquiring parts, and conducting national and international training were collected and analyzed. In total, 4047 ventilators were received by the maintenance sites, and 2516 ventilators were successfully repaired and returned to the healthcare units, which represents a success rate of 62.17%. The results show that the maintenance initiative directly impacted the availability and reliability of the equipment, allowing access to ventilators in the public and private health system and increasing the capacity of beds during the pandemic.
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- 2021
27. Microstructure and cyclic oxidation behavior of modified Nb-alloyed A297 HH refractory austenitic stainless steel
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Flavio Soldera, Frank Mücklich, Pedro Paiva Brito, P.A. Ramos, Rodrigo Santiago Coelho, and Haroldo Cavalcanti Pinto
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Austenite ,Materials science ,Scanning electron microscope ,Metallurgy ,technology, industry, and agriculture ,Niobium ,Oxide ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,0104 chemical sciences ,Carbide ,chemistry.chemical_compound ,Chromium ,chemistry ,engineering ,General Materials Science ,Austenitic stainless steel ,0210 nano-technology - Abstract
The modified ASTM A297 Gr. HH austenitic stainless steels are a group of refractory alloys designed for high temperature applications that required elevated mechanical strength, such as those found in petrochemical furnace structures and in the steel industry. This study examines the overall microstructural features and cyclic oxidation behaviour of modified HH steels with 0.09%Nb and 0.77%Nb additions. The investigations involved thermodynamic simulations and microstructure analyses conducted by optical and scanning electron microscopy of the substrate materials in the as-cast and aged conditions. The cyclic oxidation tests were performed at 900 °C in atmospheric conditions with oxidation times up to 960h. The resulting oxide scales were analyzed by X-ray diffraction and scanning electron microscopy. The thermodynamic simulations and microstructure analyses of the as-cast steels revealed larger amounts of niobium carbides in the 0.77%Nb steel than in the 0.09%Nb steel, in connection with larger amounts of chromium in solution. Despite this precipitation difference, no significant changes were noticed in the long-term oxidation behaviour of the tested materials.
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- 2021
28. Microstructural features of dynamic recrystallization in alloy 625 friction surfacing coatings
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Rodrigo Santiago Coelho, Stefanie Hanke, Ian Araújo Camões Sena, and Jorge Fernandez dos Santos
- Subjects
010302 applied physics ,Equiaxed crystals ,Materials science ,Mechanical Engineering ,Metallurgy ,Recrystallization (metallurgy) ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Industrial and Manufacturing Engineering ,Grain size ,Maschinenbau ,Coating ,Mechanics of Materials ,0103 physical sciences ,engineering ,Dynamic recrystallization ,General Materials Science ,Severe plastic deformation ,0210 nano-technology ,Electron backscatter diffraction - Abstract
In friction surfacing (FS), material is deposited onto a substrate in the plasticized state, using frictional heat and shear stresses. The coating material remains in the solid state and undergoes severe plastic deformation (SPD) at high process temperatures (≈0.8 Tmelt), followed by high cooling rates in the range of 30 K/s. Dynamic recrystallization and the thermal cycle determine the resulting microstructure. In this study, Ni-based alloy 625 was deposited onto 42CrMo4 substrate, suitable, for instance, for repair welding of corrosion protection layers. Alloy 625 is known to undergo discontinuous dynamic recrystallization under SPD, and the resulting grain size depends on the strain rate. The coating microstructure was studied by microscopy and electron backscatter diffraction (EBSD). The coatings exhibit a fully recrystallized microstructure with equiaxed grains (0.5–12 µm) and a low degree of grain average misorientation. Flow lines caused by a localized decrease in grain size and linear alig...
- Published
- 2017
29. Tensile Stress Analyses through Digital Image Correlation of Single Lap Joints of High Strength Steel and Aluminum Alloy Using Adhesive Bonding
- Author
-
Uwe Reisgen, Rodrigo Santiago Coelho, P.A.M.G.P. Bamberg, Bernd Marx, and Josiane Dantas Viana Barbosa
- Subjects
Digital image correlation ,Materials science ,Adhesive bonding ,Mechanical Engineering ,030206 dentistry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Stress (mechanics) ,03 medical and health sciences ,0302 clinical medicine ,Lap joint ,Mechanics of Materials ,Ultimate tensile strength ,Shear stress ,General Materials Science ,Adhesive ,Composite material ,0210 nano-technology ,Tensile testing - Abstract
Structural adhesives methods for joining multi material sheets have been focus of studies and researches for the last years. The most common and widely known type of test is the tensile test of single lap joints (SLJ). However, there are opportunities for analyzing the mechanical performance of such method in SLJ with materials of different properties, such as ductile structural aluminum alloys and high strength steels. It’s also known that the stress state of SLJ, when stressed longitudinally, generates secondary forces. One of them is known as cleavage force which initially leads to the failure of bonded joints. The aim of this work is to analyze the stress state of similar and dissimilar materials SLJ submitted to tensile stresses and also the influence of some variables, such as overlap length, adhesive film thickness and adherend yield limit, over the stress strength of the samples. As adherend materials it was selected the structural aluminum alloy AA 5083 H111 and the high strength steel DP600. At the end of this work it is expected to understand the proper stress state of the SLJ when using similar and dissimilar materials, identifying stress concentrators that bring the structure to fail, using the Digital Image Correlation (DIC) method. It was discovered that the yield strength associated with the overlap length highly influences the SLJ strength, by leading it to a close to pure adhesive shear stress state.
- Published
- 2016
30. Analysis of Pre-Strain in a Hybrid Forming Process Including Stretch and Incremental Sheet Forming
- Author
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Rodrigo Santiago Coelho, F.A. Lora, Lirio Schaeffer, and Bruno Caetano dos Santos Silva
- Subjects
Work (thermodynamics) ,Engineering drawing ,Materials science ,Computer simulation ,Mechanical Engineering ,Process (computing) ,Forming processes ,Condensed Matter Physics ,Mechanics of Materials ,Pre strain ,visual_art ,visual_art.visual_art_medium ,General Materials Science ,Deep drawing ,Composite material ,Sheet metal ,Incremental sheet forming - Abstract
The conventional sheet metal forming processes, such as deep drawing and stretch forming, are used to produce large batches of parts, however they incur in higher initial manufacturing costs attributed to the use of a large amount of tooling. The application of conventional and incremental forming processes combined in the same metal sheet is called hybrid forming. This hybrid process is enacted by pre-forming the sheet through the stretch forming process followed by the final manufacture using the incremental process. The objective of this work is to analyze the influence of the pre-strain imposed during the conventional process on the DC04 steel relative to the maximum strain obtained. A numerical simulation was used to define the parameters for the conventional process and to evaluate the experimental results. The higher major true strains are inversely proportional to the pre-strain in both experimental and simulated results.
- Published
- 2016
31. Histological data of axons, astrocytes, and myelin in deep subcortical white matter populations
- Author
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Meghdoot Mozumder, Julie E. Simpson, Paul G. Ince, Marina Costantini, Jose M. Pozo, Santiago Coelho, J. Robin Highley, and Alejandro F. Frangi
- Subjects
0303 health sciences ,Pathology ,medicine.medical_specialty ,Multidisciplinary ,Biology ,lcsh:Computer applications to medicine. Medical informatics ,White matter ,03 medical and health sciences ,Myelin ,0302 clinical medicine ,medicine.anatomical_structure ,Ageing ,medicine ,lcsh:R858-859.7 ,lcsh:Science (General) ,Subcortical lesions ,030217 neurology & neurosurgery ,Neuroscience ,030304 developmental biology ,Diffusion MRI ,lcsh:Q1-390 - Abstract
This immunohistochemistry dataset contains the main structures in deep subcortical white matter (axons, astrocytes, and myelinated axons) in a representative cohort of an ageing population. A set of samples from 90 subjects of the Cognitive Function and Ageing Study (CFAS) were analysed, stratified into three groups of 30 subjects each, in relation to the presence of age-associated deep subcortical lesions. High-resolution microscopy data enables the extraction of valuable information, such as volume fractions, for the construction and validation of diffusion MRI (dMRI) models. The dataset provided here was used in Coelho et al. [1].
- Published
- 2019
32. Quantitative histomorphometry of capillary microstructure in deep white matter
- Author
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Meghdoot Mozumder, Julie E. Simpson, Marina Costantini, Santiago Coelho, Jose M. Pozo, J. Robin Highley, Paul G. Ince, and Alejandro F. Frangi
- Subjects
Male ,Aging ,Cognitive Neuroscience ,Population ,lcsh:Computer applications to medicine. Medical informatics ,050105 experimental psychology ,lcsh:RC346-429 ,Microcirculation ,White matter ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Humans ,Single-Blind Method ,0501 psychology and cognitive sciences ,Radiology, Nuclear Medicine and imaging ,education ,Vascular dementia ,lcsh:Neurology. Diseases of the nervous system ,Aged ,Aged, 80 and over ,education.field_of_study ,medicine.diagnostic_test ,business.industry ,05 social sciences ,Regular Article ,Magnetic resonance imaging ,medicine.disease ,Magnetic Resonance Imaging ,White Matter ,Hyperintensity ,Capillaries ,medicine.anatomical_structure ,Neurology ,Cerebral blood flow ,Cerebrovascular Circulation ,lcsh:R858-859.7 ,Female ,Neurology (clinical) ,business ,Perfusion ,030217 neurology & neurosurgery ,Biomedical engineering - Abstract
White matter lesions represent a major risk factor for dementia in elderly people. Magnetic Resonance Imaging (MRI) studies have demonstrated cerebral blood flow reduction in age-related white matter lesions, indicating that vascular alterations are involved in developing white matter lesions. Hypoperfusion and changes in capillary morphology are generally linked to dementia. However, a quantitative study describing these microvascular alterations in white matter lesions is missing in the literature; most previous microvascular studies being on the cortex. The aim of this work is to identify and quantify capillary microstructural changes involved in the appearance of deep subcortical lesions (DSCL). We characterize the distribution of capillary diameter, thickness, and density in the deep white matter in a population of 75 elderly subjects, stratified into three equal groups according to DSCL: Control (subject without DSCL), Lesion (sample presenting DSCL), and Normal Appearing White Matter (NAWM, the subject presented DSCL but not at the sampled tissue location). Tissue samples were selected from the Cognitive Function and Aging Study (CFAS), a cohort representative of an aging population, from which immunohistochemically-labeled histological images were acquired. To accurately estimate capillary diameters and thicknesses from the 2D histological images, we also introduce a novel semi-automatic method robust to non-perpendicular incidence angle of capillaries into the imaging plane, and to non-circular deformations of capillary cross sections. Subjects with DSCL presented a significant increase in capillary wall thickness, a decrease in the diameter intra-subject variability (but not in the mean), and a decrease in capillary density. No significant difference was observed between controls and NAWM. Both capillary wall thickening and reduction in capillary density contribute to the reduction of cerebral blood flow previously reported for white matter lesions. The obtained distributions provide reliable statistics of capillary microstructure useful to inform the modeling of human cerebral blood flow, for instance to define microcirculation models for their estimation from MRI or to perform realistic cerebral blood flow simulations. Keywords: Vascular dementia, Deep white matter, Deep subcortical lesion, Capillary microstructure
- Published
- 2019
33. Influence of shot peening on residual stresses and tribological behavior of cast and austempered ductile iron
- Author
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Haroldo Cavalcanti Pinto, Klaus Higor dos Santos Silva, Pedro Paiva Brito, José Rubens Gonçalves Carneiro, and Rodrigo Santiago Coelho
- Subjects
Hard metal ,Materials science ,Metallurgy ,TENSÃO RESIDUAL ,02 engineering and technology ,Surfaces and Interfaces ,Tribology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,Shot peening ,Hardness ,Surfaces, Coatings and Films ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,Casting (metalworking) ,Materials Chemistry ,Surface roughness ,0210 nano-technology ,Austempering - Abstract
Austempered ductile irons exhibit an interesting combination of properties such as low cost, elevated strength, fatigue and wear resistance. In the present contribution, the influence of shot-peening on the dry-sliding wear behavior of as-cast and austempered ductile irons was evaluated. Specimens from a casting with an initial ferritic-pearlitic matrix were submitted to austempering at 320 °C for 60 min after which an ausferritic microstructure with 40 HRC and approximately 30% retained austenite was obtained. The wear and friction behaviors were assessed by applying ball-on-disc tests using a hard metal (WC) counter-body on as-cast and austempered materials before and after shot-peening and after removal of the rough surface layer created by the shot-peening process. The microstructure of the tested materials was evaluated by X-ray diffraction, optical and scanning electron microscopy. After shot-peening, the austempered samples experienced an elevated increase in surface hardness because of the formation of strain-induced martensite, but a reduction in wear resistance caused by the increase in surface roughness. By removing 20 μm from the surface of the shot-peened samples, it was possible to reduce roughness while preserving the hardened layer, which was found to improve wear resistance.
- Published
- 2019
34. Optimal Experimental Design for Biophysical Modelling in Multidimensional Diffusion MRI
- Author
-
Santiago Coelho, Jose M. Pozo, Sune Nørhøj Jespersen, and Alejandro F. Frangi
- Subjects
Noise (signal processing) ,Computer science ,Brain tissue ,Inverse problem ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,symbols.namesake ,0302 clinical medicine ,Metric (mathematics) ,symbols ,Tensor ,Fisher information ,Algorithm ,030217 neurology & neurosurgery ,Eigenvalues and eigenvectors ,Diffusion MRI - Abstract
Computational models of biophysical tissue properties have been widely used in diffusion MRI (dMRI) research to elucidate the link between microstructural properties and MR signal formation. For brain tissue, the research community has developed the so-called Standard Model (SM) that has been widely used. However, in clinically applicable acquisition protocols, the inverse problem that recovers the SM parameters from a set of MR diffusion measurements using pairs of short pulsed field gradients was shown to be ill-posed. Multidimensional dMRI was shown to solve this problem by combining linear and planar tensor encoding data. Given sufficient measurements, multiple choices of b-tensor sets provide enough information to estimate all SM parameters. However, in the presence of noise, some sets will provide better results. In this work, we develop a framework for optimal experimental design of multidimensional dMRI sequences applicable to the SM. This framework is based on maximising the determinant of the Fisher information matrix, which is averaged over the full SM parameter space. This averaging provides a fairly objective information metric tailored for the expected signal but that only depends on the acquisition configuration. The optimisation of this metric can be further restricted to any subclass of desirable design constraints like, for instance, hardware-specific constraints. In this work, we compute the optimal acquisitions over the set of all b-tensors with fixed eigenvectors.
- Published
- 2019
35. ESTUDO COMPUTACIONAL DA ESTAMPABILIDADE DE AÇO INOXIDÁVEL ATRAVÉS DA SIMULAÇÃO NUMÉRICA DO ENSAIO DE CINCO PUNÇÕES
- Author
-
Rodrigo Santiago Coelho, Fábio André Lora, and Marcelo Sousa de Carvalho
- Published
- 2018
36. Local volume fraction distributions of axons, astrocytes, and myelin in deep subcortical white matter
- Author
-
Paul G. Ince, Jose M. Pozo, Julie E. Simpson, J. Robin Highley, Santiago Coelho, Meghdoot Mozumder, Alejandro F. Frangi, and Marina Costantini
- Subjects
Male ,0301 basic medicine ,Pathology ,medicine.medical_specialty ,Cognitive Neuroscience ,Neuropathology ,Biology ,White matter ,03 medical and health sciences ,Myelin ,0302 clinical medicine ,Image Processing, Computer-Assisted ,medicine ,Humans ,Axon ,Myelin Sheath ,Aged, 80 and over ,Brain ,White Matter ,Axons ,Hyperintensity ,030104 developmental biology ,medicine.anatomical_structure ,Neurology ,Ageing ,Astrocytes ,Volume fraction ,Female ,030217 neurology & neurosurgery ,Diffusion MRI - Abstract
This study aims to statistically describe histologically stained white matter brain sections to subsequently inform and validate diffusion MRI techniques. For the first time, we characterise volume fraction distributions of three of the main structures in deep subcortical white matter (axons, astrocytes, and myelinated axons) in a representative cohort of an ageing population for which well-characterized neuropathology data is available. We analysed a set of samples from 90 subjects of the Cognitive Function and Ageing Study (CFAS), stratified into three groups of 30 subjects each, in relation to the presence of age-associated deep subcortical lesions. This provides volume fraction distributions in different scenarios relevant to brain diffusion MRI in dementia. We also assess statistically significant differences found between these groups. In agreement with previous literature, our results indicate that white matter lesions are related with a decrease in the myelinated axons fraction and an increase in astrocytic fraction, while no statistically significant changes occur in axonal mean fraction. In addition, we introduced a framework to quantify volume fraction distributions from 2D immunohistochemistry images, which is validated against in silico simulations. Since a trade-off between precision and resolution emerged, we also performed an assessment of the optimal scale for computing such distributions.
- Published
- 2018
37. In situ assessment of isochronal phase transformations in a lamellar Ti–5Al–5Mo–5V–3Cr–1Zr alloy using synchrotron X-ray diffraction
- Author
-
Flavio Soldera, Pedro Paiva Brito, Haroldo Cavalcanti Pinto, Bruna Callegari, Katherine Aristizabal, Lucia Campo, María Agustina Guitar, Rodrigo Santiago Coelho, Frank Mücklich, and Fernando Gustavo Warchomicka
- Subjects
Materials science ,Precipitation (chemistry) ,Mechanical Engineering ,Alloy ,Metals and Alloys ,Analytical chemistry ,02 engineering and technology ,Atom probe ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Isothermal process ,0104 chemical sciences ,law.invention ,Mechanics of Materials ,law ,Transmission electron microscopy ,Phase (matter) ,Materials Chemistry ,engineering ,Grain boundary ,Lamellar structure ,0210 nano-technology - Abstract
Phase transformations in a lamellar Ti–5Al–5Mo–5V–3Cr–1Zr (Ti-55531) alloy upon heating at continuous rates of 5, 20 and 100 °C/min has been studied by in situ high energy X-ray diffraction (HEXRD), aided by scanning and transmission electron microscopy, atom probe tomography and hardness measurements. During slow heating, the β phase has shown a behavior suggestive of additional transformations other than the continuous α → β decomposition observed at higher heating rates. Such behavior has been attributed to the precipitation of an embryonic isothermal ω phase. APT analyses have shown that no elemental partitioning occurs between the β matrix and the lamellar α phase, but it does between β and grain boundary α, suggesting that ω phase precipitates with solute rejection in regions outside lamellar colonies embedded in an enriched matrix. Above 500 °C, diffusion becomes significantly enhanced and α decomposition takes place.
- Published
- 2021
38. Residual stress analysis in thermally grown oxide scales developed on Nb-alloyed refractory austenitic stainless steels
- Author
-
Rodrigo Santiago Coelho, Flavio Soldera, F. Mücklich, Haroldo Cavalcanti Pinto, Pedro Paiva Brito, and P.A. Ramos
- Subjects
Austenite ,Materials science ,020209 energy ,General Chemical Engineering ,Metallurgy ,technology, industry, and agriculture ,Refractory metals ,Oxide ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,Thermal expansion ,Corrosion ,chemistry.chemical_compound ,chemistry ,Residual stress ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,Spallation ,0210 nano-technology - Abstract
Reliable high temperature operation of refractory metals depends on the mechanical integrity of the protective oxide formed on the material surface. The residual stress state in oxide layers developed on two modified Nb-alloyed ASTM A297 HH austenitic stainless steels, thermal expansion analysis of the substrate, steel microstructure, oxide layers morphology and phases composition were analyzed. The experimental analyses revealed that larger Nb additions increased NbC precipitates, which was connected to lower thermal expansion coefficient of the substrate. Despite similarities in the oxide scales, the higher Nb-alloyed samples exhibited lower magnitude residual stress values and larger spallation after long-term oxidation.
- Published
- 2021
39. Analysis of the GTAW Process Influence on UNS S32760 Superduplex Steel Microstructure and Corrosion Resistance
- Author
-
Matheus Rian da Silva Almeida, Rodrigo Santiago Coelho, Lílian Lefol Nani Guarieiro, and Raphael Oliveira dos Santos
- Subjects
Materials science ,Scientific method ,Gas tungsten arc welding ,Metallurgy ,General Chemistry ,Microstructure ,Corrosion - Published
- 2016
40. New insights into the microstructural evolution of Ti-5Al-5Mo-5V-3Cr alloy during hot working
- Author
-
João Pedro Oliveira, Bruna Callegari, N. Schell, José Garcia, Flavio Soldera, F. Mücklich, Rodrigo Santiago Coelho, Pedro Paiva Brito, M.I. Sadik, and Haroldo Cavalcanti Pinto
- Subjects
010302 applied physics ,Materials science ,Misorientation ,Mechanical Engineering ,Alloy ,02 engineering and technology ,engineering.material ,Strain rate ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Hot working ,ddc:670 ,Mechanics of Materials ,0103 physical sciences ,engineering ,Thermomechanical processing ,General Materials Science ,DIFRAÇÃO POR RAIOS X ,Texture (crystalline) ,Composite material ,Deformation (engineering) ,0210 nano-technology ,Electron backscatter diffraction - Abstract
Microstructural features resulting from thermomechanical treatment of the β-metastable Ti-5Al-5Mo-5V-3Cr (Ti-5553) alloy were studied by means of electron backscatter diffraction and X-ray diffraction. The alloy was deformed at 950 °C (β field) and 800 °C (α + β field) with strain rates of 0.001 s−1 and 0.1 s−1 in compression mode up to a compression ratio of 0.5 (true ratio = 0.7). It was concluded that β phase undergoes dynamic recovery both above and below its β-transus temperature, and recovery is more dominant at lower strain rates, which was corroborated by EBSD misorientation measurements. Meanwhile, α phase undergoes not only a process of breakage and globularization, but also decomposition, which contributes to flow softening. The increase in strain rate caused non-uniform recovery at 950 °C and a more intense refinement of α precipitates at 800 °C. Macrotexture evaluation after deformation indicates that β's texture is much stronger than that of α, with its (200) component being the strongest one.
- Published
- 2020
41. Iba-1-/CD68+ microglia are a prominent feature of age-associated deep subcortical white matter lesions
- Author
-
Daniel J. Fillingham, Paul G. Ince, Santiago Coelho, Meghdoot Mozumder, Jose M. Pozo, Lynne Baxter, Rachel Waller, Alejandro F. Frangi, J. Robin Highley, and Julie E. Simpson
- Subjects
0301 basic medicine ,Central Nervous System ,Pathology ,Aging ,Serum Proteins ,Glycobiology ,Immunostaining ,Microgliosis ,Alzheimer's Disease ,Biochemistry ,Nervous System ,Basement Membrane ,0302 clinical medicine ,Animal Cells ,Medicine and Health Sciences ,Cognitive decline ,Myelin Sheath ,Staining ,education.field_of_study ,Multidisciplinary ,Microglia ,Microfilament Proteins ,Neurodegenerative Diseases ,Immunohistochemistry ,White Matter ,Extracellular Matrix ,DNA-Binding Proteins ,medicine.anatomical_structure ,Aquaporin 4 ,Neurology ,Blood-Brain Barrier ,Medicine ,Cellular Types ,Anatomy ,Cellular Structures and Organelles ,Research Article ,medicine.medical_specialty ,Science ,Population ,Antigens, Differentiation, Myelomonocytic ,Glial Cells ,Biology ,Blood–brain barrier ,Research and Analysis Methods ,White matter ,03 medical and health sciences ,Antigens, CD ,Mental Health and Psychiatry ,medicine ,Humans ,Cognitive Dysfunction ,education ,Cell Shape ,Microglial Cells ,Immunohistochemistry Techniques ,Glycoproteins ,Calcium-Binding Proteins ,Histocompatibility Antigens Class II ,Biology and Life Sciences ,Fibrinogen ,Proteins ,Cell Biology ,Hyperintensity ,Histochemistry and Cytochemistry Techniques ,030104 developmental biology ,Specimen Preparation and Treatment ,Immunologic Techniques ,Dementia ,030217 neurology & neurosurgery ,Biomarkers - Abstract
Deep subcortical lesions (DSCL) of the brain, are present in ~60% of the ageing population, and are linked to cognitive decline and depression. DSCL are associated with demyelination, blood brain barrier (BBB) dysfunction, and microgliosis. Microglia are the main immune cell of the brain. Under physiological conditions microglia have a ramified morphology, and react to pathology with a change to a more rounded morphology as well as showing protein expression alterations. This study builds on previous characterisations of DSCL and radiologically 'normal-appearing' white matter (NAWM) by performing a detailed characterisation of a range of microglial markers in addition to markers of vascular integrity. The Cognitive Function and Ageing Study (CFAS) provided control white matter (WM), NAWM and DSCL human post mortem tissue for immunohistochemistry using microglial markers (Iba-1, CD68 and MHCII), a vascular basement membrane marker (collagen IV) and markers of BBB integrity (fibrinogen and aquaporin 4). The immunoreactive profile of CD68 increased in a stepwise manner from control WM to NAWM to DSCL. This correlated with a shift from small, ramified cells, to larger, more rounded microglia. While there was greater Iba-1 immunoreactivity in NAWM compared to controls, in DSCL, Iba-1 levels were reduced to control levels. A prominent feature of these DSCL was a population of Iba-1-/CD68+ microglia. There were increases in collagen IV, but no change in BBB integrity. Overall the study shows significant differences in the immunoreactive profile of microglial markers. Whether this is a cause or effect of lesion development remains to be elucidated. Identifying microglia subpopulations based on their morphology and molecular markers may ultimately help decipher their function and role in neurodegeneration. Furthermore, this study demonstrates that Iba-1 is not a pan-microglial marker, and that a combination of several microglial markers is required to fully characterise the microglial phenotype.
- Published
- 2018
42. Resolving degeneracy in diffusion MRI biophysical model parameter estimation using double diffusion encoding
- Author
-
Santiago Coelho, Alejandro F. Frangi, Jose M. Pozo, Derek K. Jones, and Sune Nørhøj Jespersen
- Subjects
microstructure imaging ,Mean squared error ,Models, Neurological ,single diffusion encoding ,030218 nuclear medicine & medical imaging ,diffusion MRI ,03 medical and health sciences ,0302 clinical medicine ,biophysical tissue models ,Image Processing, Computer-Assisted ,Applied mathematics ,Radiology, Nuclear Medicine and imaging ,Computer Simulation ,Diffusion (business) ,Mathematics ,Full Paper ,Estimation theory ,Noise (signal processing) ,Feasible region ,Invariant (physics) ,3. Good health ,double diffusion encoding ,Diffusion Magnetic Resonance Imaging ,Full Papers—Biophysics and Basic Biomedical Research ,Degeneracy (mathematics) ,parameter estimation ,white matter ,030217 neurology & neurosurgery ,Algorithms ,Diffusion MRI - Abstract
Purpose: Biophysical tissue models are increasingly used in the interpretation of diffusion MRI (dMRI) data, with the potential to provide specific biomarkers of brain microstructural changes. However, it has been shown recently that, in the general Standard Model, parameter estimation from dMRI data is ill‐conditioned even when very high b‐values are applied. We analyze this issue for the Neurite Orientation Dispersion and Density Imaging with Diffusivity Assessment (NODDIDA) model and demonstrate that its extension from single diffusion encoding (SDE) to double diffusion encoding (DDE) resolves the ill‐posedness for intermediate diffusion weightings, producing an increase in accuracy and precision of the parameter estimation. Methods: We analyze theoretically the cumulant expansion up to fourth order in b of SDE and DDE signals. Additionally, we perform in silico experiments to compare SDE and DDE capabilities under similar noise conditions. Results: We prove analytically that DDE provides invariant information non‐accessible from SDE, which makes the NODDIDA parameter estimation injective. The in silico experiments show that DDE reduces the bias and mean square error of the estimation along the whole feasible region of 5D model parameter space. Conclusions: DDE adds additional information for estimating the model parameters, unexplored by SDE. We show, as an example, that this is sufficient to solve the previously reported degeneracies in the NODDIDA model parameter estimation.
- Published
- 2018
43. Estudo dos Efeitos da Deformação Plástica na Microestrutura e na Dureza do Titânio Comercialmente Puro
- Author
-
Rodrigo Santiago Coelho and Raoni Barreto de Oliveira
- Published
- 2018
44. Gerenciamento de risco em poluição
- Author
-
Waldir Macho La Rubbia, Renata Bazante Yamaguishi, Francisco Carlos Paletta, Josimar Ribeiro de Almeida, Afonso Rodrigues de Aquino, Renan Braga Ribeiro, Felipe de Moura Kiiper, Ernesto Díaz Rocha, Isabela Cristina Antunes Bordon, Maria José Alves de Oliveira, Sandra Regina Mattiolo, Joaquim Matheus Santiago Coelho, Renata Medeiros Lobo Muller, Leandro Augusto Pidone, Caio Roberto Picolomini Buongermino, Gustavo Sousa Affonso, Dymes Rafael Alves dos Santos, Ana Luiza Fávaro Piedade, and Verônica Araujo Boemer
- Published
- 2017
45. Riscos ambientais urbanos
- Author
-
Afonso Rodrigues de Aquino, Ernesto Díaz Rocha, Leandro Augusto Pidone, Dymes Rafael Alves dos Santos, Felipe de Moura Kiiper, Caio Roberto Picolomini Buongermino, Renan Braga Ribeiro, Josimar Ribeiro de Almeida, Renata Medeiros Lobo Muller, Isabela Cristina Antunes Bordon, Francisco Carlos Paletta, Sandra Regina Mattiolo, Maria José Alves de Oliveira, Waldir Macho La Rubbia, Ana Luiza Fávaro Piedade, Verônica Araujo Boemer, Gustavo Sousa Affonso, Joaquim Matheus Santiago Coelho, and Renata Bazante Yamaguishi
- Published
- 2017
46. Avaliação de risco ambiental de ecossistemas aquáticos
- Author
-
Gustavo Sousa Affonso, Dymes Rafael Alves dos Santos, Leandro Augusto Pidone, Maria José Alves de Oliveira, Francisco Carlos Paletta, Isabela Cristina Antunes Bordon, Afonso Rodrigues de Aquino, Ernesto Díaz Rocha, Felipe de Moura Kiiper, Josimar Ribeiro de Almeida, Ana Luiza Fávaro Piedade, Joaquim Matheus Santiago Coelho, Renata Medeiros Lobo Muller, Renan Braga Ribeiro, Sandra Regina Mattiolo, Waldir Macho La Rubbia, Caio Roberto Picolomini Buongermino, Renata Bazante Yamaguishi, and Verônica Araujo Boemer
- Published
- 2017
47. Análise de riscos ambientais no derramamento de petróleo
- Author
-
Renan Braga Ribeiro, Renata Medeiros Lobo Muller, Leandro Augusto Pidone, Sandra Regina Mattiolo, Joaquim Matheus Santiago Coelho, Ana Luiza Fávaro Piedade, Maria José Alves de Oliveira, Felipe de Moura Kiiper, Verônica Araujo Boemer, Afonso Rodrigues de Aquino, Isabela Cristina Antunes Bordon, Ernesto Díaz Rocha, Francisco Carlos Paletta, Gustavo Sousa Affonso, Caio Roberto Picolomini Buongermino, Dymes Rafael Alves dos Santos, Renata Bazante Yamaguishi, Josimar Ribeiro de Almeida, and Waldir Macho La Rubbia
- Published
- 2017
48. Biomarcadores e o processo de avaliação de risco ambiental
- Author
-
Renata Bazante Yamaguishi, Leandro Augusto Pidone, Caio Roberto Picolomini Buongermino, Isabela Cristina Antunes Bordon, Gustavo Sousa Affonso, Maria José Alves de Oliveira, Afonso Rodrigues de Aquino, Ernesto Díaz Rocha, Renan Braga Ribeiro, Renata Medeiros Lobo Muller, Sandra Regina Mattiolo, Waldir Macho La Rubbia, Josimar Ribeiro de Almeida, Felipe de Moura Kiiper, Verônica Araujo Boemer, Dymes Rafael Alves dos Santos, Joaquim Matheus Santiago Coelho, Ana Luiza Fávaro Piedade, and Francisco Carlos Paletta
- Published
- 2017
49. Gerenciamento de risco para equipamentos eletroeletrônicos e eletromédicos
- Author
-
Renata Bazante Yamaguishi, Ana Luiza Fávaro Piedade, Caio Roberto Picolomini Buongermino, Leandro Augusto Pidone, Josimar Ribeiro de Almeida, Isabela Cristina Antunes Bordon, Waldir Macho La Rubbia, Renan Braga Ribeiro, Verônica Araujo Boemer, Joaquim Matheus Santiago Coelho, Sandra Regina Mattiolo, Dymes Rafael Alves dos Santos, Francisco Carlos Paletta, Felipe de Moura Kiiper, Afonso Rodrigues de Aquino, Ernesto Díaz Rocha, Gustavo Sousa Affonso, Renata Medeiros Lobo Muller, and Maria José Alves de Oliveira
- Published
- 2017
50. Riscos ambientais empresariais
- Author
-
Francisco Carlos Paletta, Renan Braga Ribeiro, Renata Medeiros Lobo Muller, Josimar Ribeiro de Almeida, Sandra Regina Mattiolo, Caio Roberto Picolomini Buongermino, Leandro Augusto Pidone, Afonso Rodrigues de Aquino, Ana Luiza Fávaro Piedade, Isabela Cristina Antunes Bordon, Ernesto Díaz Rocha, Maria José Alves de Oliveira, Felipe de Moura Kiiper, Dymes Rafael Alves dos Santos, Waldir Macho La Rubbia, Renata Bazante Yamaguishi, Gustavo Sousa Affonso, Joaquim Matheus Santiago Coelho, and Verônica Araujo Boemer
- Published
- 2017
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