bluuebunny/crossref_metadata_2025 huggingface dataset:
Drawings, Proofs and Prints from the Qianlong Emperor’s East Turkestan Copperplate Engravings
Authors: Leverenz Niklas
Published: August 2016

At the command of the Qianlong emperor, Chinese troops conquered a vast territory in Central Asia in three campaigns between 1755 and 1759, greatly expanding the Qing empire. The emperor commemorated these victories in several ways, including the commission of a set of sixteen copperplate prints that were ultimately produced for the Qing court by engravers in Paris. These engravings, justifiably famous in their own time, continue to attract the attention of scholars and collectors. Recent publications in China and Europe, as well as the availability of archival documents in French and Chinese shed new light on the production of the “Conquest” engravings, one of the First and surely the most important, examples of cultural collaboration between China and Europe before modern times. This article describes the creation of the model drawings in China and the production process of the copperplate engravings and prints in France with reference to three contemporary 18th-century French publications. It further examines the existing proof prints and lists the extant sets of prints in different versions in museum and library collections as well as prints that have appeared in auction sales worldwide.
Floral scent of Joshua trees (Yucca brevifolia sensu lato): Divergence in scent profiles between species but breakdown of signal integrity in a narrow hybrid zone
Authors: Svensson Glenn P. , Raguso Robert A. , Flatz Ramona , Smith Christopher I.
Published: August 2016

PREMISE OF THE STUDY:

The role of floral scent in facilitating reproductive isolation between closely related plants remains poorly understood. Yucca brevifolia and Yucca jaegeriana are pollinated by different moth species in allopatry, but in a narrow contact zone, pollinator–host specificity breaks down, resulting in hybridization between species. We explored the chemical basis for reproductive isolation and hybridization in these Joshua trees by characterizing the floral scent of each species in allopatry, analyzing scent profiles from trees in the contact zone, and matching these data with genotypic and phenotypic data.

METHODS:

We analyzed floral volatiles using gas chromatography–mass spectrometry, tested for species divergence of scent profiles and classified trees in the contact zone as hybrid or either parental species. We used floral and vegetative morphological data and genotypic data to classify trees and analyzed whether certain trait combinations were more correlated than others with respect to assignment of trees and whether frequencies of classified tree types differed depending on which data set was used.

KEY RESULTS:

The Joshua tree floral scent included oxygenated 8‐carbon compounds not reported for other yuccas. The two species differed (P < 0.001) in scent profiles. In the contact zone, many hybrids were found, and phenotypic traits were generally weakly correlated, which may be explained by extensive gene flow between species or by exposure to different selection pressures.

CONCLUSIONS:

Although the two Joshua tree species produce distinct floral scent profiles, it is insufficient to prevent attraction of associated pollinators to both hosts. Instead, floral morphology may be the key trait mediating gene flow between species.
Serum 25-hydroxyvitamin D status in pregnant women with chronic hepatitis B virus infection
Authors: Gao Xue-ren , Wang Cui-min , Wang Wen-jun , Han Guo-rong , Zhang Jian-qiong
Published: August 2016

Introduction: Maternal 25-hydroxyvitamin D [25(OH)D] deficiency has a negative influence on the health of the mother and the developing fetus. The aim of this study was to assess serum 25(OH)D status and its relationship to virologic and biochemical parameters in pregnant women with chronic hepatitis B virus (HBV) infection. Methodology: Serum 25(OH)D levels among 142 pregnant women with chronic HBV infection and 251 healthy pregnant women were measured using enzyme-linked immunosorbent assay. Results: The mean ± SD values for serum 25(OH)D levels were 13.63 ± 5.5 ng/mL in healthy pregnant women and 12.05 ± 3.3 ng/mL in pregnant women with chronic HBV infection (p < 0.01). Serum 25(OH)D levels were associated with seasonal variation in healthy pregnant women (p = 0.01); however, similar results were not observed in pregnant women with chronic HBV infection (p = 0.10). Furthermore, multivariate analysis indicated that only ALT level was independently associated with severe vitamin D deficiency (p = 0.01). A significant positive correlation was found between serum 25(OH)D level and ALT level in pregnant women with chronic HBV infection (r = 0.32; p < 0.001). Conclusions: Vitamin D levels were lower in pregnant women with chronic HBV infection compared with healthy pregnant women. Vitamin D supplementation can be routinely recommended for pregnant women in China.
Use of Flaviviral genetic fragments as a potential prevention strategy for HIV-1 Silencing
Authors: Sheraz Muhammad , Kanak Mazhar , Hasan Mahmudul , Bhattarai Roshan , Mahalingam Kuhanandha , Sealey Leanna A , Blackwood Rashshana R , Golkar Zhabiz , McLean Ewen , Bagasra Omar
Published: August 2016

Introduction: Coinfection with certain members of the Flaviviridae, such as Dengue Virus (DV), West Nile Virus (WNV) Yellow Fever Virus (YFV) and most importantly, GBV-C have been documented to reduce HIV-1 viral load in vivo. Numerous studies strongly support the notion that persistent coinfection with non-pathogenic virus prolongs survival in HIV-1 infected individuals. Coinfected individuals show higher CD4+ cell counts, lower HIV-1 RNA viral loads and live three times longer than clinically matched HIV-1 monoinfected patients. We have previously shown that one of the major anti-HIV defenses conferred by GBV-C coinfection is the upregulation of intracellular miRNAs in CD4+ cells that share significant mutual homologies with GBV-C and HIV-1 (>80%) genomes. Methodology: Genome-wide bioinformatics analyses were carried out to search for miRNA binding sites in mutual homologies between HIV and several members of the Flaviviridae Results:  Several miRNAs shared significant mutual homology with HIV-1 genetic sequences and GBV-A, B, C, DV, WNV and YFV.  These may be responsible for beneficial effects in HIV-1 infected individuals. Three highly mutual homologous miRNAs (i.e. miR-627-5, miR-369-5 and miR-548f), expressed in CD4+ cell lines, reduce HIV-1 replication by up to 90% whereas miRNAs with low mutual homologies (i.e. miR-34-1 and miR-508) impart only slight inhibition of HIV-1. Conclusion: We hypothesize that a recombinant GBV-C-based vector can be constructed which expresses several beneficial genetic motifs of the Flaviviridae without causing any side effects while stimulating a wide array of beneficial miRNAs that can more efficiently prevent HIV-1 infection.
Absence of poliovirus in apparently healthy school children in Bauchi state, Nigeria
Authors: Nasir Idris Abdullahi , Shehu Muhammad Sagir , Thairu Yunusa
Published: August 2016

Introduction: Poliovirus infections have been established to be in circulation in the remaining three polio-endemic nations. These pathogens have been associated with several chronic diseases, particularly acute flaccid paralysis of children. This study sought to ascertain whether polioviruses are silently shed by apparently healthy schoolchildren in Bauchi, Katagum, and Misau local government areas of Bauchi state, Nigeria. Methodology: This was a cross-sectional prospective study that involved 200 stool samples collected from apparently healthy schoolchildren. All samples were processed and inoculated onto rhabdomyosarcoma (RD) and L20B cell-lines. Inoculated cell lines were monitored for cytopathic effects (CPEs) for 10 days with one subculture after first 5 days. Results: None of the samples came down with CPEs on L20B, and thus all samples were negative for poliovirus; however, three were positive for non-polio enteroviruses (NPEVs) on RD and not on the L20B cell line: one coxsackie B virus from a seven-year-old male, and two others were untypeable isolates, one each from a male and a female child. The coxsackie B virus was identified by microneutralization test using polyclonal sera as described by the World Health Organization. Conclusions: Findings from this investigation indicate the absence of polioviruses in the children studied. This is an indication of good polio immunization coverage in these communities. However, more intensive and periodic surveillance is required to confirm the presence or exclude the absence of polioviruses in these communities and other parts of Nigeria.
Análise da Produção Escrita em Avaliação sobre Sistemas de Numeração e Código BCD
Authors: Ramos Maria Luisa Perdigao Diz , Curi Edda
Published: August 2016

Este artigo tem como objetivo classificar e analisar a produção escrita em uma questão que abrange representação numérica em diferentes sistemas de numeração e em código BCD. Essa questão faz parte de uma avaliação aplicada a 38 alunos do 1º ano do curso técnico de uma escola pública de Minas Gerais. A metodologia usada neste trabalho foi a análise de conteúdo da produção escrita em cada um dos quatro itens que compõem a questão. Para isso, as respostas foram classificadas como corretas, parcialmente corretas e incorretas. Com o resultado, foi possível constatar que a maioria dos alunos é capaz de representar um número em diferentes sistemas de numeração, mas comete erros ao representar esse número no código BCD. Isso se deve ao fato de eles não compreenderem que, para representar um número em BCD, primeiramente, esse número precisa estar representado em decimal e, posteriormente, ser representado em BCD.
Transgênicos, conformismo e consumo: algumas reflexões para o Ensino de Ciências
Authors: Genovese Cinthia Leticia Carvalho Roversi , Genovese Luiz Gonzaga Roversi , Carvalho Washington Luiz Pacheco de
Published: August 2016

O objetivo deste trabalho é discutir a controvérsia sobre os transgênicos e a aparente aceitação dos consumidores brasileiros a esses alimentos, sob a ótica de alguns conceitos da Teoria Crítica de Horkheimer e Adorno (1985), como esclarecimento e Indústria Cultural. Posteriormente, argumentamos a importância da formação de professores, para que eles auxiliem os estudantes na busca de uma cidadania plena, autônoma e crítica. Neste sentido, propomos o estudo de questões controversas, como os transgênicos, que envolvem a ciência e a sociedade em nossas escolas. Tais questões são conhecidas como questões sociocientíficas (QSC).
Avaliação de conceitos de termodinâmica clássica através de mapas conceituais
Authors: Oliveira Guilherme Cordeiro da Graça de , Santos Paula Macedo Lessa dos , Almeida Rodrigo Dos Santos
Published: August 2016

Neste trabalho o mapeamento conceitual foi utilizado para avaliação de conceitos de termodinâmica clássica, numa turma do curso de Engenharia Química da Universidade Federal do Rio de Janeiro, como parte da primeira avaliação da disciplina. Foi proposto aos alunos que construíssem um mapa conceitual com 8 conceitos obrigatórios e, no máximo, 4 conceitos complementares. A metodologia empregada na avaliação dos mapas elaborados pelos alunos consistiu na contagem e análise das proposições. Os principais objetivos foram: (i) investigar a aplicação dos mapas conceituais como instrumento de avaliação dos conteúdos de termodinâmica clássica; (ii) avaliar as proposições construídas pelos alunos e (iii) investigar a percepção dos alunos com relação à metodologia de avaliação utilizando mapas conceituais. Os resultados permitiram concluir que os alunos apresentaram uma boa compreensão dos conceitos investigados, porém identificaram também concepções errôneas em desacordo com a visão científica. Entrevistas semiestruturadas revelaram uma boa aceitação da metodologia de avaliação através de mapas conceituais.
Proposta de uma Metodologia de Ensino de Espaços Vetoriais
Authors: Figueroa Teodora Pinheiro , Almouloud Saddo Ag
Published: August 2016

O trabalho apresenta uma proposta de metodologia para o ensino de Espaço Vetorial. Essa proposta é fundamentada na Teoria das Situações Didáticas de Brousseau e na Teoria dos Registros de Representações de Duval. As sequências didáticas foram planejadas de forma a criar condições para o aluno ter uma atitude autônoma durante todo o processo de construção do conceito de Espaço Vetorial. O objetivo fundamental deste trabalho é mostrar que as interações do aluno com situações didáticas apropriadas e um certo milieu são essenciais para o aluno construir o conceito de forma significativa, sendo capaz de um elevado nível de abstração. O objetivo foi atingido, o que se pode comprovar através dos resultados obtidos.
Contribuição da Web 2.0 como ferramenta de aprendizagem: um estudo de caso
Authors: Leite Bruno Silva , Leão Marcelo Brito Carneiro
Published: August 2016

Este trabalho tem como propósito de analisar e avaliar a utilização de alguns recursos da Web 2.0, e como esses estão sendo inseridos no ensino das ciências. Apresentamos um estudo sobre uma experiência em que um grupo de alunos trabalhou com algumas ferramentas da Web 2.0 durante uma disciplina de Química, envolvendo a temática de ligações Químicas. Nosso objetivo foi de analisar o papel de algumas ferramentas da Web 2.0 e como estas poderiam contribuir para uma aprendizagem ampla e flexível por parte desses usuários. Utilizamos também para fins desta investigação, a observação de um grupo de alunos que não se utilizaram dessas ferramentas, visando uma comparação com o grupo de usuários Web 2.0. Dentre os resultados obtidos, ressaltamos o potencial de ajuda das ferramentas Web 2.0, descrita pelos alunos. Observamos também a importância da incorporação da Teoria da Flexibilidade Cognitiva e da Teoria dos Construtos Pessoais em ambiente Web 2.0 para a construção de uma aprendizagem mais flexível.
Questões contemporâneas e desenvolvimento de aplicativos móveis: onde está a conexão?
Authors: Batista André Luiz França , Bazzo Walter Antônio
Published: August 2016

Em consequência das discussões sobre estudos Ciência, Tecnologia e Sociedade (CTS) verificou-se a necessidade de entender como promover discussões sobre esses assuntos em uma disciplina de programação de dispositivos móveis. O objetivo deste artigo é mostrar como é possível inserir assuntos pertinentes aos problemas da sociedade em uma disciplina de enfoque altamente técnico. Desse modo o presente trabalho detém um enfoque informativo e torna-se um possível subsídio para auxílio a professores que pretendam estabelecer discussões CTS em suas classes de programação computacional móvel. As sugestões aqui documentadas caracterizam-se como recursos para um provável aprimoramento do pensamento crítico e conduta cidadã dos discentes e para o fomento de discussões e reflexões, entre educadores e futuros profissionais, sobre a realidade vigente, ensejando iminentes mudanças educacionais.
Meeting Education Needs of Flexible Staffing: Begin With the End in Mind
Authors: Schindler Jaclyn S.
Published: August 2016

In our multicenter organization, we prepare personnel to practice at consistent levels of excellence. Centralized orientation programs facilitate sharing best practice and collective vision. When acute needs for care delivery occur, traditional orientation is not feasible. Regardless of staffing model or training methodology, performance at the bedside must be equal.

J Contin Educ Nurs.
2016;47(9):390–392.
Influence of Time and Temperature on Directional Growth of MoO3
Authors: Ferreira da Silva Claudia , Lima e Silva André , Nobre Francisco Xavier , Silva Filho Edson Cavalcanti , Santos Jr. Luiz de Sousa , Santos Maria Rita de Morais Chaves , de Matos José Milton Elias
Published: August 2016

Two-dimensional microstructures of molybdenum trioxide (MoO3) were synthesized by heptamolybdate tetrahydrate ammonium acidification, followed by calcination. A solution of the precursor compound heptamolybdate tetrahydrate ammonium acidified to pH 3,5 using glacial acetic acid followed by hydrothermal treatment for 150, 180 and 200 °C for 1, 6 and 12 hours. Then, the intermediate was calcined at 300 °C for varying time 6 and 12h to obtain MoO3. X-ray diffraction revealed that the crystals grew with crystalline structure corresponding to the orthorhombic phase of MoO3 (a-MoO3) as major phase, with a preferential growth direction along the planes (0K0). Raman spectroscopy and IR confirmed the formation of the characteristic modes of molybdenum trioxide for stage found. With Scanning Electron Microscopy (SEM) was possible to observe the formation of nanoplates.
Determining the Content of Toxic Substances in Panels from Pruning Acacia mangium Willd
Authors: Nery de Souza João Sammy , Barbosa Furtini Marcelo , Silva Filho Edson Cavalcanti , Abreu Yara Karolynne Lopes , de Sousa Wanderson Araujo , de Araújo Francisca Pereira , Guimarães Jr. José Benedito , Osajima Josy Anteveli
Published: August 2016

The objective of this study was to determine the content of free formaldehyde contained in panels of Acacia mangium clippings. The results of the analysis show that the best temperature for a Hantzschen reaction is 60°C. The panels had a linear behavior over the course of the exposure time (168 hours), whereas samples with a lower surface area showed linearity starting at 72 hours. Thus, it is possible to quantify the emission of formaldehyde panels, thereby supporting research to create measures that minimize its release.
Influence of Weather Exposure on Dimensional Changes in Clay Ceramics Incorporated with Granite Residue
Authors: Alexandre Jonas , de Azevedo Afonso Rangel Garcez , de Castro Xavier Gustavo , Muylaert Margem Frederico , Monteiro Sergio Neves , de Oliveira Braga Fabio , de Azeredo Neila Gondim , Bozzi Piazzarollo Carla
Published: August 2016

Ceramic materials such as bricks and tiles used in civil construction, may eventually be exposed to weather conditions and undergo degradation with time. Although this degradation has been studied in common plain ceramics, it has not yet been investigated in clay ceramics incorporated with ornamental stone residues. In the present work the degradation suffered by clay ceramics incorporated with 5 and 10 wt % of a granite residue under weathering for 6, 8 and 10 months was evaluated. The incorporated and plain ceramics were fired at temperatures of 500, 700 and 900°C. The linear dimensional changes were measured just after firing as well as after 180, 240 and 300 days, respectively, 6, 8 and 10 months. In general, the linear dimensions tend to increase with time and firing temperature. The role of absorbed water on these changes is discussed.
Production Speed and its Influence on Hue Variation on Tiles Decoration Based on Silicon Cylinder Technique Laser Engraving Method
Authors: Ferraço Fabio , Boschi Anselmo Ortega , Storion Ana Gabriela
Published: August 2016

On the ceramic tile production there are plenty of different possible origins inside the process that can lead to hue variation. Many tile producers use to increase the speed of production and the machinery industry follow this tendency to please their costumers; and so this scenario creates a need of a study on the influence of the speed production on hue variation. In this work this influence was verified using the silicon laser engraving method, one of the most methods worldwide used.
Purification Route of Pyrite from Coal Mining
Authors: Machado de Oliveira Camila , Oliveira Adilson , do Rosário Jeane Almeida , de Noni Jr. Agenor , Peterson Michael
Published: August 2016

Pyrite, mineral largely found in nature, is considered a solid waste when is obtained from the coal mining. However, can be precursor of products like: sulphur, sulphuric acid, hematite, sulphur dioxide, fertilizers and iron sulfates. Several studies also point it property of semiconduction and it use in solar cells. Increase it purity level is important for transforming it in products with more aggregate value. Thus, the present work suggests a purification route for the reduction in soluble salts in water, organics and quartz associated with pyrite from the coal mining beneficiation. The used methods were solubilization in hot water and in organic solvent (dichloromethane). Were applied XRD, FTIR, total sulphur determination, and gas helium picnometry. Comparing the results obtained for the “in nature” pyrite with the purified one, proved the efficiency of the proposed method.
Synthesis of Ceramic Pigment Based on Crystal Structure of Wollastonite
Authors: Folgueras Marilena Valadares , Albuquerque G.B. , Prim S.R.
Published: August 2016

In the ceramic industry, color is of great importance to product development. Parameters such as hue, brightness and color intensity influence the visual appearance of the ceramic surface and its market value. Research on the development of new pigments is ongoing, with focus on cost reduction, environmental suitability and color innovation. Different studies have shown the feasibility of using industrial by-products to obtain pigments. Many of these waste products have calcium carbonate and nickel oxides in their composition. This study investigates the synthesis of ceramic pigment with the structure of wollastonite - CaSiO3, with the use of nickel as chromophore ion. In order to evaluate the effect of adding nickel to the formation of crystalline phases X-ray diffraction was used. Particle size analysis was performed by Laser diffraction technique and a colorimetric study was conducted through the analysis of the pigment applied to a commercial enamel, by determining colorimetric parameters L*, a* and b*. The results showed that wollastonite combined with nickel acts as pigment and that its presence may interfere with the performance of new pigments depending on the nickel content and synthesis temperature.
Evaluation of the Potential of Using Quartzite Residue in Mass for the Production of Sanitary Ware
Authors: de Medeiros Paula Simone Soares , Santana L.N.L. , Silva V.J. , Neves Gelmires Araújo , Lira Hélio Lucena
Published: August 2016

Currently there is a great concern on the part of the industries with the disposal of waste generated in the production process. The quartzite processing industry generates significant amount of residue, consisting primarily of quartz. The aim of this work is to evaluate the incorporation of quartzite residue, replacing partially the quartz and feldspar, in ceramic mass used in the production of sanitary ware. The raw materials were characterized by chemical and particle size analysis. Compositions were formulated by varying the amount of residue and comparing with an industrial mass, consisted of clay, kaolin, feldspar and quartz. The slip casting process was used in the preparation of the specimens. The results showed that the residue can be considered as an alternative raw material for use in sanitary ware industry, since the ceramic slip presented appropriate rheological properties and after firing process the specimens presented physical and mechanical properties according to the specifications.
Chemical Treatment and Characterization of Fiber of Babassu Coconut Epicarp (Orbignya phalerata) for Application in Polymeric Composite
Authors: Fonteles Carlos Alberto Lopes , Brito Gustavo Figueiredo , Reis Sobrinho José Francisco , Alves Tatianny Soares , Barbosa Renata
Published: August 2016

This set of mechanical properties of plant fibers allows its use as a reinforcement element in polymeric matrices and composites can be used in various sectors, and thus expanding the scope of use and the aggregate value of plant fibers. In this work, the choice by the use of alkali process to make the treatment of epicarp babassu fibers was decided in view of that it provides an effective, simple and low cost implementation process and also for being the most widely used method for modifying the surface of the fiber forming polymer composites. By SEM, it was observed the removal of wax layers, the impurities on the fiber surface and tyloses. With alkali treatment, it was also possible to notice the narrowing and closing of craters due to the packaging of denser material.
Bending Mechanical Behavior of Epoxy Matrix Reinforced with Buriti Fiber
Authors: Barbosa Anderson de Paula , Altoé Giulio Rodrigues , Loiola Rômulo Leite , Muylaert Margem Frederico , de Oliveira Braga Fabio , Monteiro Sergio Neves
Published: August 2016

Environmentally correct composites, made from natural fibers, are among the most investigated and applied today. In this paper, the mechanical behavior of epoxy matrix composites reinforced with continuous buriti fiber, through bending tensile tests was investigated. Specimens containing 0, 10, 20 and 30% in volume of buriti fiber were aligned along the entire length of a mold to create plates of these composites. The plates were cut following the ASTM standard to obtained bending test specimens. The test was conducted in an Instron Machine and the fractured specimens were analyzed by SEM. The results showed an increase in the materials flexural properties with the increase in volume fraction of buriti fiber.
Tensile Behavior of Epoxy Composites Reinforced with Thinner Sisal Fibers
Authors: Araújo Rohen Lazaro , Cerqueira Neves Anna Carolina , Muylaert Margem Frederico , Vieira Carlos Maurício Fontes , de Oliveira Braga Fabio , Monteiro Sergio Neves
Published: August 2016

The use of natural fibers as reinforcement in polymer matrix composites is replacing the use of synthetic fibers, especially from an environmental standpoint. Indeed, natural fibers are biodegradable and renewable, with no aggression to the environment. Moreover, they are worldwide abundant with relatively low cost. It was found that fine fibers of sisal, with the thinnest diameters can achieve tensile strength on the order of 1000 MPa. In this work, tensile specimens were prepared with 30% in volume of sisal fibers with diameters between 0.1 and 0.10mm incorporated in a continuous and aligned way into epoxy matrix. The results showed a significant increase in tensile strength and elastic modulus of the composites as a function of the incorporated amount of thinner sisal fibers.
Under Pressure Processed Polyester Composites with High Amount of Curaua Fibers for Improved Tensile Properties
Authors: Barcelos Mariana Azevedo , Tonini Simonassi Noan , Muylaert Margem Frederico , de Oliveira Braga Fabio , Monteiro Sergio Neves
Published: August 2016

Polymeric composites incorporated with natural fibers are today being used in many applications that include engineering components, for example, in the automobile industry. Among the many natural fibers, the one extracted from the curaua plant was found to be a strong reinforcing material for polymer composites. Attempts have been made to obtain stronger composites reinforced with curaua fibers. In the present work, the tensile properties of polyester matrix composites reinforced with different amounts of curaua fibers were evaluated. Composites prepared under pressure and reinforced with up to 60% in volume of long, continuous and aligned curaua fibers were tensile tested. The results showed a significant increase in the mechanical properties with the amount of curaua fiber. Those properties were found to be significantly higher as compared with other bend-tested curaua fiber composites results.
Evaluation of Biodegradability of a Compost Obtained from Polymeric Composite Reinforced Natural Fibers
Authors: de Araujo Marina J.F. , de Araujo Marcus Vinicius F. , Mulinari Daniella Regina
Published: August 2016

The aim of this study was to develop a sustainable composter that works associating aerobic digestion of organic matter from waste to anaerobic digestion of that organic matter. The composter was developed from a composite of polyester resin reinforced with palm fibers to contribute to the waste generated in the consumption of palm in Brazilian territory. Moreover, biodegradation of the developed composite was studied in contact with the organic material deposited in the composter. Results showed that the composter has potential to generate good quality organic compost for fertilization and also showed that the composite in contact with the organic matter reduced mechanical properties of the material.
Differential Scanning Calorimetry Tests of Epoxy and Polyester Composites Reinforced with Giant Bamboo Fibers
Authors: Oliveira Glória Gabriel , de Moraes Ygor Macabu , Ribeiro Carolina Gomes Dias , de Souza Martins Lucas Barboza , Muylaert Margem Frederico , de Oliveira Braga Fabio , Monteiro Sergio Neves
Published: August 2016

Despite the benefits associated with the use of natural fibers instead of synthetic ones as composite reinforcement, there are still some limitations to their application. Among the disadvantages associated with natural fibers stands the low thermal resistance. This imposes restrictions to the composite utilization when it is exposed to temperatures above 100 oC. For one point, the hydrophilic nature of lignocellulosic fibers causes absorption of water, but at high temperatures this water is lost, what produce pores and flaws in the composite polymer matrix. Moreover, the fiber cellulose, hemicellulose and lignin are degraded at higher temperatures. The objective of the present work was to conduct a comparative differential scanning calorimetric investigation between polyester and epoxy matrixes composites incorporated with different volume fractions of giant bamboo fibers. A substantial loss of mass was found up to 120 oC. The DSC curves revealed a variation in the enthalpy as a function of the giant bamboo fiber fractions and the corresponding polymeric matrix.
Stress Cracking Analysis on Automotive Tubes Made with Polyamide 12
Authors: Polkowski Rodrigo , Melo Pollyana , Pisanu Luciano
Published: August 2016

The mechanism of Environmental Stress Cracking (ESC) in polymers results from the interaction of three main elements: susceptible material, stress condition and a specific environment. The wide range of possible combinations of those three variables is what makes the ESC very difficult to predict and resolve. Therefore, this article intends to analyze the behavior of regions under stress of automotive tubes made with polyamide 12 exposed to a common degreaser material. Samples were manufactured through extrusion process and conditioned to different levels of stress before being exposed to the action of degreaser. The test results showed that aggressive fluids, like degreasing liquids, can be considered as catalysts of the Environmental Stress Cracking phenomenon in automotive tubes of polyamide 12.
Preparation and Characterization of Composites Obtained of Polymeric Waste Coming from Boards Electronic Equipment
Authors: Magnago Roberto de Oliveira , Mulinari Daniella Regina , do Amaral Monique Pacheco , Rodrigues Luciano Monteiro , dos Santos Claudinei
Published: August 2016

The objective of this work is to recycle the printed circuit boards of electronic equipment discarded and mix them with polypropylene (PP) to produce a new composite. Six types of mix of discarded printed circuit boards were analyzed: new boards with and without copper, used boards without components and with and without copper, used boards without components and without copper, used boards with copper track, used boards with copper track and burned and used boards with components. Boards were disintegrated and employed as reinforcement with polypropylene matrix (5% m/m). Specimens were produced for flexural and impact tests. Results showed that specimen’s properties depend on the mix composition. In all of the cases, pure PP properties were enhanced when it was replaced by 5% of waste materials discard.
Effect of Hydrolytic Degradation on Mechanical Properties of PCL
Authors: França Danyelle Campos , Bezerra Elieber Barros , Morais Dayanne Diniz Souza , Araújo Edcleide Maria , Wellen Renate Maria Ramos
Published: August 2016

This work investigated the effect of hydrolytic degradation on mechanical properties in tension and impact strength of poly (Ɛ-caprolactone) (PCL). PCL specimens produced by injection processing were submersed in water and exposed at 40°C into a vacuum heater. The specimens were collected from the heater after periods of 15, 30 and 45 days, respectively, followed by mechanical tests. According to the data acquired for Elastic Modulus, specimens exposed for 15 and 45 days presented a decrease of 9.65% and 13.65%; for Yield Stress a decrease of 9.08% and 10.38% was observed at same period of time compared with unexposed specimens. Concerning the Elongation at Break tests unexposed PCL reached the maximum limit of machine without fracturing while exposed specimens had their elongation at break capability decreased. Unexpected results were observed for the specimens exposed for 30 days which presented an increase of 3.43%, 3.12% and 5.88% for Elastic Modulus, Yield Stress and Strength at Break. Impact Strength presented similar trend to that of mechanical properties in tension. It is suggested that these trends are connected with morphological changes which took place in the amorphous and crystalline phases of PCL during hydrolytic degradation.
Study of Damage in the Medium Density Polyethylene Using Digital Image Correlation
Authors: dos Santos Lindemberg Ferreira , de Codes Rodrigo Nogueira , Silva Erijanio Nonato , de Codes Rodrigo Amaral
Published: August 2016

The non-linear response of solids is an expression of irreversible processes that originate in microdefects, which are understood as initial material damage. This work aims to analyze the degradation of the mechanical properties of medium density polyethylene through continuum damage mechanics using Digital Image Correlation (DIC). With this technique, displacement and strain fields are obtained throughout the specimen gauge length and therefore optical gauges in any region of interest can measure the strain. Mechanical testing with successive loading and unloading were performed in order to obtain the actual magnitude of the material stiffness in certain strains. Finally, through the damage versus strain diagrams, the results showed that the damage in medium density polyethylene increases from a certain deformation.
Tensile Test of High Strength Thinner Curaua Fiber Reinforced Polyester Matrix Composite
Authors: Monteiro Sergio Neves , Muylaert Margem Frederico , Tonini Simonassi Noan , Loiola Rômulo Leite , Picanço Oliveira Michel
Published: August 2016

In recent years natural fibers, especially those lignocellulosic extracted from plants, have gained attention owing to their engineering performance as polymer composite reinforcement. It was found that some of these lignocellulosic fibers, such as the curaua, ramie and sisal may reach tensile strength above 1000 MPa in association with very thin diameters. Therefore. the objective of the present work was to fabricate polyester matrix composites with the highest tensile strength possible, by reinforcing with the thinnest continuous and aligned curaua fibers. Tensile tests results of composites reinforced with 30% volume of these thinnest curaua fibers showed a tensile strength of 135 MPa, which corresponds to one of the highest strength attained for lignocellulosic fiber composites.
Pullout Tests Behavior of Polyester Matrix Reinforced with Malva Fiber
Authors: Margem Jean Igor , Alves Gomes Vinicius , Muylaert Margem Frederico , Ribeiro Carolina Gomes Dias , de Oliveira Braga Fabio , Monteiro Sergio Neves
Published: August 2016

The interface between a composite matrix and the reinforcing fiber plays an important role in the efficiency by which an applied load is transmitted throughout the composite structure. The shear stress at the fiber/matrix interface can be associated with this load transference and, consequently, will affect the composite strength. In the present work, pullout tests were used to evaluate the interfacial shear stress of malva fiber in polyester matrix composites. A small critical length was found for the malva fiber embedded in polyester, which corresponds to a relatively weak fiber/matrix bond and lower interfacial strength.
Fabrication of Polypyrrole Nanoparticles Using Microemulsion Polymerization for Diferent Py/APS/SDS Molar Ratios
Authors: Santim Ricardo Hidalgo , de Aquino Hermes Adolfo , Malmonge José Antonio
Published: August 2016

Polypyrrole nanoparticles (PPy) were synthesized by the chemical oxidative microemulsion of pyrrole (Py) monomer using ammonium persulfate (APS) as an oxidant agent and sodium dodecylsulfate (SDS) as a surfactant at 28°C and 0°C. Different Py:APS:SDS molar ratios were used, and the properties of the resulting material were examined by four-probe DC electrical conductivity, ultraviolet-visible-near infrared (UV-vis-Nir), and Fourier-transform infrared (FTIR) spectroscopies as well as field-emission scanning electron microscopy (FESEM). UV-vis-Nir and FTIR spectra show the formation of a polaron band owing to the doping of PPy by SDS. The electrical conductivity and morphology of PPy nanoparticles depend on the synthesis conditions. Electrical conductivity of ~95.3×10-3 S/cm was achieved for PPy synthesized at 0°C. For the same Py:APS:SDS molar ratio, the nanoparticle shape changed from cylindrical to spherical upon simply lowering the synthesis temperature.
Application of Computational Thermodynamics to the Evolution of Surface Tension and Gibbs-Thomson Coefficient during Multicomponent Aluminum Alloy Solidification
Authors: Jácome Paulo A.D. , Fernandes Marcio T. , Garcia Amauri , Ferreira Alexandre F. , de Castro José Adilson , Ferreira Ivaldo Leão
Published: August 2016

Numerical simulation of multicomponent alloy solidification demands accuracy of thermophysical properties in order to obtain a numerical representation as close as possible to the physical reality. Some alloy properties are only seldom found in the literature. In this paper, a solution of Butler’s formulation for surface tension is presented for Al-Cu-Si ternary alloys, allowing the Gibbs-Thomson coefficient to be calculated as a function of Cu and Si contents. The importance of the Gibbs-Thomson coefficient is related to the reliability of predictions furnished by predictive microstructure growth models and of numerical computations of solidification thermal variables that will be strongly dependent on the values of the thermophysical properties adopted in the calculations. A numerical model based on Powell hybrid algorithm and a finite difference Jacobian approximation was coupled with a ThermoCalc TCAPI interface to assess the excess Gibbs energy of the liquid phase, permitting the surface tension and Gibbs-Thomson coefficient for Al-Cu-Si hypoeutectic alloys to be calculated. The computed results are presented as a function of the alloy composition.
Friction Stir Welding of Aluminium Alloy Sheets
Authors: Vale N.L. , Dos Santos Jorge Fernandez , Melo I.R. , Araújo Filho Oscar Olimpio , Urtiga Filho Severino Leopoldino
Published: August 2016

Aluminium alloy 7050 in a T7451 temper was friction-stir welded (FSW) to investigate the effects of different process parameters on the microstructure and mechanical properties. Butt joints were obtained in 10mm thick-sheets, keeping a constant rotational speed of 550 rpm. Weld power and torque were recorded for each weld in order to obtain the heat input of the process, since the final properties of the welds are strongly related to this variable. The joints were characterized by optical microscopy and microhardness indentation through the stir zone (SZ), thermo-mechanically affected zone (TMAZ), and heat affected zone (HAZ) at different cross section heights. The processing of FSW, the microstructure in FSW alloys and the factors influencing weld quality are introduced.
Manufacturing and Characterization of AA1100 Aluminum Alloy Metal Matrix Composites Reinforced by Silicon Carbide and Alumina Processed by Powder Metallurgy
Authors: Araújo Filho Oscar Olimpio , Araújo de Moura Alexandre Douglas , de Araújo Everthon Rodrigues , dos Santos Maurílio José , Gonzalez Cezar Henrique , da Silva Flávio José
Published: August 2016

Powder Metallurgy (PM) Techniques consists in a suitable technique to process composites materials. A specific PM technique of mechanical alloying developed to produce new materials in the solid state is a consolidated route to obtain aluminum alloys metal matrix composites. Aluminum alloys metal matrix composites allies the good properties of aluminum and its alloys but with poor mechanical properties and the reinforcement of ceramics phases which add better mechanical properties to these alloys. The research of this materials processing by PM techniques presented new materials with improved properties. In this work an AA1100 aluminum alloy was reinforced by particulate silicon carbide and alumina types of ceramic phases. The powders were mixed and then processed by mechanical alloying in a SPEX vibratory type mill. Then the powders obtained were compacted and vacuum sintered. The sintered composites were characterized by means of Scanning Electron Microscopy (SEM) plus Energy Dispersive Spectroscopy (EDS) and Vickers hardness (HV) tests to evaluate the mechanical behavior.
Comparative Analysis of Fracture Toughness Obtained by Different Techniques in Alumina Matrix - Dispersed TZP Zirconia Composites
Authors: Nono Daniel Alessander , Fernandes da Silva Eron , Nono Maria do Carmo de Andrade , Neto Francisco Piorino , Mineiro Sergio Luiz
Published: August 2016

The fracture toughness is one of the requirements for mechanical properties of materials for use in satellites. The ceramic TZP zirconia (tetragonal zirconia polycrystals) have been investigated for applications in ballistic armor. Due to the chemical inertness and fracture toughness, this material has the potential to act as a screen against impacts of micrometeorites and space debris. The ceramic composites of alumina-zirconia 3Y-TZP (tetragonal zirconia polycrystals doped with 3 mol% ytria ) are the materials with the best benefit / cost for this application. This paper presents and discusses the results obtained from the use of two techniques for determining fracture toughness. The composite alumina - 18.5% of 3Y-TZP zirconia nanoparticles obtained from deflocculated powders have been tested for Vickers and the SEVNB penetration method (Single-Edge-Notch Beam V) to obtain the fracture toughness values (KIC). The KIC values obtained were analyzed due to the lower dispersion of experimental values. The SEVNB method showed better reliability in determining the toughness values in the studied ceramics.
Crystallization of Amorphous Cu49.7Ti31.8Zr11.3Ni7.2 Alloy
Authors: Triveño Rios Carlos , Contieri R.
Published: August 2016

Bulk metallic glasses are attractive materials for structural and functional applications when compared to crystalline materials. The Cu-based glasses exhibit particular interest due primarily to their relatively low cost and high fracture resistance. In this work the Cu49.7Ti31.8Zr11.3Ni7.2 alloy was prepared from the mixture of pure metals by arc melting and following the ingot was re-melted by centrifugal casting in wedge-section copper mould. The structure of wedge bulk sample was evaluated by a combination of X-Ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). The results show that the amorphous state is formed in the thinner region and it is maintained up to thickness of 3.5 mm in the wedge bulk-sample. The crystallization temperature was observed above 400 °C coinciding with the studies of thermal crystallization by XRD and DSC. Dynamical heating of the amorphous phase from room temperature up to 750°C showed the formation of CuTi, Cu10Zr7 e Cu2TiZr crystalline phases.
Influence of Heat Treatment on Martensitic Transformations in Copper-Based Alloys with Shape Memory Effect
Authors: Sekitani da Silva Luiz Carlos , Gonzalez Cezar Henrique , do Nascimento Oliveira Carlos Augusto , da Silva Karla Carolina Alves
Published: August 2016

In the present work the copper base alloys with shape memory effects were characterized. The alloys were subjected to three different heat treatments that promoted changes in characteristics of thermoelastic martensitic transformation (transformation temperatures, thermal hysteresis and enthalpies of transformation). The alloys have their microstructures characterized by optical and scanning electron microscopy. Microhardness tests were performed. Differential scanning calorimetry (DSC) was used to evaluate the transformation critical temperatures of alloy and the transformation enthalpies for each heat treated sample. Thermoelastic properties have changed for each heat treatment. In the micrographs of the heat-treated samples was possible to observe the microstructure of the martensitic phase characteristic. They show the presence of martensite platelets (needles) self-accommodation.
Strain-Induced Martensite Formation of AISI 304L Steel Sheet: Experiments and Modeling
Authors: Costa D.C.T. , Cardoso M.C. , da Fonseca Gláucio S. , Moreira Luciano Pessanha , Martiny M. , Mercier S.
Published: August 2016

Metastable austenitic stainless steels are prone to strain-induced martensite transformation (SIMT) during deformation at room temperature, as in the case of sheet metal forming processes. The SIMT is influenced by the chemical composition, grain size, temperature, deformation mode or stress state and strain-rate. In this work, interrupted and continuous uniaxial tensile tests were performed in AISI 304L sheet to evaluate the SIMT as a function of strain and strain-rate effects. The SIMT was evaluated by feritscope and temperature in-situ measurements and both XRD and optical microscopy techniques. The SIMT kinetics was also investigated by means of thermo-mechanical finite element simulations using a phenomenological model. In the small strain range, the yield stress increases with the strain-rate whereas in the large strain domain a cross-effect in the stress-strain curve is observed given that the SIMT is inhibited due to the specimen heat generation. A very good correlation between XRD and feritscope measurements was found from the interrupted uniaxial tensile testing. The finite element numerical simulations allowed to identify the parameters of a phenomenological model which describes the SIMT kinetics of AISI 304L steel sheet as a function of plastic-strain, strain-rate and temperature effects.
The Effect of Phase Transformation on the Tensile Fracture of Austenitic Stainless Steel
Authors: Scarpini Cândido Verônica , Monteiro Sergio Neves
Published: August 2016

The tensile fracture of two austenitic stainless steels with different degrees of stability for low temperature strain induced martensitic transformation was investigated. A stable AISI type 310 stainless steel displayed typical tensile stress-strain curves with decreasing work hardening rate at temperatures in the interval of 25 to-196°C, in which no martensitic transformation occurred. By contrast, a metastable type 302 stainless steel with martensitic transformation from 25 to-196°C showed a range of plastic deformation with increasing work hardening rate. The fracture of the stable 310 steel presented the characteristic cup and cone ductile aspect with micro dimples and sparse evidence of intergranular cracks. On the contrary, the martensitic transformation in the metastable 302 steel causes a neckless fracture with generally brittle appearance, despite the relatively high strain attained at fracture. At-80 and-196°C, associated with higher amount of transformed martensite, the fracture surface was covered with micro-craters formed around inclusions enveloped by thin strain induced martensite lamellae.
Evaluation of Cracking Susceptibility of Weldment Container for Nuclear Power Plant
Authors: Monteiro Sergio Neves , Tedesco Bolzan Lucas , Muylaert Margem Frederico
Published: August 2016

The cracking susceptibility of a WSTE-51 steel for pressurized container of a nuclear power plant was evaluated. This evaluation was performed by means of the Controlled Thermal Severity Test and the Cold Cracking TEKKEN Test, as well as the VINCKIER Test for reheating cracking. Conventional mechanical tests and metallographic examinations were performed to characterize additional properties of the welding. The results indicated that the weldment has susceptibility to crack formation. Procedures to avoid this susceptibility were discussed.