Three-dimensional numerical simulation of Vickers indentation tests

The development of depth sensing indentation equipment has allowed easy and reliable determination of two of the most popular measured mechanical properties of materials: the hardness and the Young's modulus. However, some difficulties emerge in the experimental procedure to calculate accurate values of these properties. This is related to, for example, the tip geometrical imperfections of the diamond pyramidal indenter and the definition of the contact area at the maximum load. Being so, numerical simulation of ultramicrohardness tests can be a helpful tool for better understanding of the influence of these parameters on procedures for determining the hardness and the Young's modulus. For this purpose, specific finite element simulation software, HAFILM, was developed to simulate the ultramicrohardness tests. Different mesh refinements were tested because of the dependence between the values of the mechanical properties and the size of the finite element mesh. Another parameter studied in this work is the value of the friction coefficient between the indenter and the sample in the numerical simulation. In order to obtain numerical results close to reality, a common geometry and size of the imperfection of the tip of Vickers indenter was taken into account for the numerical description of the indenter.http://www.sciencedirect.com/science/article/B6VJS-4FXNRM9-2/1/fc471d8e5a726ca5ef37aaf842f333c

AINFO versão 5.0: manual on-line.

Introdução; Conhecendo o AINFO; Gerenciador de Dados e outros procedimentos especiais; Administrando o AINFO; Atualizando as bases de dados; Sobre as bases de dados; Imprimindo relatórios; Sobre o SIR - Recuperação de Informação; Descrição dos campos; Descrição dos relatórios; Anexos.bitstream/CNPTIA/11296/1/doc62.pdf2. ed. rev. atual.Acesso em: 28 maio 2008

AINFO - versão 5.0: manual on-line.

O AINFO é um sistema para automação de bibliotecas e recuperação de informação, desenvolvimento em padrão Windows, com arquitetura cliente/servidor baseada no sistema gerenciador de banco de dados relacional Firebird. Pemite o gerenciamento de informação técnico-científica, integrando bases de dados documentais, cadastrais e processos bibliográficos através do armazenamento, atualização, indexação e recuperação de informação de forma simples e rápida, utilizando não apenas recursos de um istema gerenciador de banco de dados, como controle de concorrência e manutenção de integridade das bases de dados, mas também oferecendo facilidades de recuperação de informação textual não disponíveis nesses sistemas.bitstream/CNPTIA/10207/1/doc40.pdfAcesso em: 29 maio 2008

Biodegradable poly(L-lactic acid) scaffolds with internal hyaluronic acid coating. biological response in vitro

[Excerpt] Poly(L-lactic acid), a synthetic biodegradable polyester, is widely accepted for many tissue engineering applications. Hyaluronic acid (HA), as a polysaccharide of the extra cellular matrix (ECM), besides exhibiting an excellent biocompatibility, influences cell signaling, growth and differentiation. A combination between these materials might be interesting for tissue engineering studies. However, HA must be chemically modified for this use because of its easy dissolution in water and quick degradation in biological environments. Glutaraldehyde, GA, has been proposed as crosslinking agent to produce HA hydrogels. However, accordingly to the literature, there are contradictory results about the experimental protocol to be used, and relating to the cytotoxicity caused by glutaraldehyde remaining in the sample after crosslinking reactions. [...]info:eu-repo/semantics/publishedVersio

A new approach for reverse analyses in depth-sensing indentation using numerical simulation

This paper seeks to present a new approach to reverse analysis in depth-sensing indentation which makes use of numerical simulation. This methodology allows the results of experimental hardness tests acquired with single indenter geometry to be used to determine the plastic properties of materials. Forward and reverse analyses of high deformation three-dimensional numerical simulations of Vickers indentation tests are used to determine different mechanical properties of materials: Young's modulus, yield stress and strain-hardening exponent. The Vickers indenter used in the numerical simulations is formulated as a rigid body and takes into account the presence of the most common imperfection of the tip, so-called offset. The contact friction between the Vickers indenter and the deformable body is also considered. The forward analysis uses materials with Young's modulus values from 50 to 600 GPa, yield stress values from 0.3 to 10 GPa and strain-hardening exponents from 0 to 0.6; the Poisson ratio did not vary from 0.3. The representative plastic strain [epsilon]r and the correspondent stress [sigma]r, as previously defined by other authors [Dao M, Chollacoop N, Vliet KJ, Venkatesh TA, Suresh S. Acta Mater 2001;49:3899], were identified by an independent numerical method. The values of the representative plastic strain [epsilon]r obtained for the Vickers indenter confirm those of the above-mentioned authors, despite showing a slight influence from the Young's modulus values. The forward study enables the production of a unique plot of the hardness HIT vs. representative stress [sigma]r, where both are normalized by the Young's modulus E. The proposed reverse analysis provides a unique solution to the representative stress [sigma]r and the strain-hardening exponent, n, given that the Young's modulus is predetermined from the experimental hardness test. Depending on the material properties, the value of n can be more or less sensitive to the scatter of the experimental results obtained using the depth-sensing equipment, particularly the stiffness of the unloading curve. The validity of the proposed reverse analysis method is checked using three real materials: stamping quality steel (DC 06), stainless AISI 304 steel and BK7 glass.http://www.sciencedirect.com/science/article/B6TW8-4M69JXG-1/1/ffe1726f3b7df73e4e01c941d6c4cbe

Indicações técnicas para produção de sementes de plantas recuperadoras de solo para a agricultura familiar.

bitstream/CPACT-2009-09/11809/1/documento_227.pd

Agrobiodiversidade como base para sistemas agrícolas sustentáveis para a agricultura familiar.

bitstream/item/78746/1/Documento-354.pd

Produção de semente genética de soja na Embrapa Trigo em 2014/2015.

bitstream/item/141071/1/ID43632-2015PLDocOnline155sojaresultadosp30.pd

The impact of the COVID-19 pandemic on the short-term survival of patients with cancer in Northern Portugal

The COVID-19 pandemic led to potential delays in diagnosis and treatment of cancer patients, which may negatively affect the prognosis of these patients. Our study aimed to quantify the impact of COVID-19 on the short-term survival of cancer patients by comparing a period of 4 months after the outbreak began (2 March 2020) with an equal period from 2019. All cancer cases of the esophagus, stomach, colon and rectum, pancreas, lung, skin-melanoma, breast, cervix, and prostate, from the Portuguese Oncology Institute of Porto (IPO-Porto) and diagnosed between 2 March and 1 July of 2019 (before COVID-19) and 2020 (after COVID-19) were identified. Information regarding sociodemographic, clinical and treatment characteristics were collected from the cancer registry database and clinical files. Vital status was assessed to 31 October of the respective years. Cox proportional hazards regression was used to estimate crude and propensity score-adjusted hazards ratio (HR) and 95% confidence intervals (95% CIs) of death. During follow-up to 31 October, there were 154 (11.8%) deaths observed before COVID-19 and 131 (17.2%) after COVID-19, corresponding to crude and adjusted HRs (95% CI) of 1.51 (1.20-1.91) and 1.10 (0.86-1.40), respectively. Significantly higher adjusted hazards of death were observed for patients with Stage III cancer (HR = 2.37; 95% CI: 1.14-4.94) and those undergoing surgical treatment (HR = 3.97; 95% CI: 1.14-13.77) or receiving radiotherapy (HR = 1.96; 95% CI: 1.96-3.74), while patients who did not receive any treatment had a lower mortality hazards (HR = 0.62; 95% CI: 0.46-0.83). The higher overall short-term mortality observed during the COVID-19 pandemic largely reflects the effects of the epidemic on the case-mix of patients being diagnosed with cancer.Funding information: European Regional Development Fund through the Operational Programme Competitiveness and Internationalization & Fundação para a Ciência e a Tecnologia, Grant/Award Number: POCI-01-0145-FEDER-032358; ref. PTDC/SAU-EPI/32358; Fundação para a Ciência e a Tecnologia, Grant/Award Number: info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UIDB/04750/2020/PT; Fundação para a Ciência e a Tecnologia & Agency for Clinical Research and Biomedical Innovation, Grant/Award Number: RESEARCH 4 COVID-19 174_59685054