Drilling process of composite laminates – a tool based analysis

“Drilling of polymeric matrix composites structures”

Strength improvement of adhesively-bonded joints using a reverse-bent geometry

Adhesive bonding of components has become more efficient in recent years due to the developments in adhesive technology, which has resulted in higher peel and shear strengths, and also in allowable ductility up to failure. As a result, fastening and riveting methods are being progressively replaced by adhesive bonding, allowing a big step towards stronger and lighter unions. However, single-lap bonded joints still generate substantial peel and shear stress concentrations at the overlap edges that can be harmful to the structure, especially when using brittle adhesives that do not allow plasticization in these regions. In this work, a numerical and experimental study is performed to evaluate the feasibility of bending the adherends at the ends of the overlap for the strength improvement of single-lap aluminium joints bonded with a brittle and a ductile adhesive. Different combinations of joint eccentricity were tested, including absence of eccentricity, allowing the optimization of the joint. A Finite Element stress and failure analysis in ABAQUS® was also carried out to provide a better understanding of the bent configuration. Results showed a major advantage of using the proposed modification for the brittle adhesive, but the joints with the ductile adhesive were not much affected by the bending technique.

Prevalence of chronic low back pain: systematic review

OBJECTIVE To estimate worldwide prevalence of chronic low back pain according to age and sex. METHODS We consulted Medline (PubMed), LILACS and EMBASE electronic databases. The search strategy used the following descriptors and combinations: back pain, prevalence, musculoskeletal diseases, chronic musculoskeletal pain, rheumatic, low back pain, musculoskeletal disorders and chronic low back pain. We selected cross-sectional population-based or cohort studies that assessed chronic low back pain as an outcome. We also assessed the quality of the selected studies as well as the chronic low back pain prevalence according to age and sex. RESULTS The review included 28 studies. Based on our qualitative evaluation, around one third of the studies had low scores, mainly due to high non-response rates. Chronic low back pain prevalence was 4.2% in individuals aged between 24 and 39 years old and 19.6% in those aged between 20 and 59. Of nine studies with individuals aged 18 and above, six reported chronic low back pain between 3.9% and 10.2% and three, prevalence between 13.1% and 20.3%. In the Brazilian older population, chronic low back pain prevalence was 25.4%. CONCLUSIONS Chronic low back pain prevalence increases linearly from the third decade of life on, until the 60 years of age, being more prevalent in women. Methodological approaches aiming to reduce high heterogeneity in case definitions of chronic low back pain are essential to consistency and comparative analysis between studies. A standard chronic low back pain definition should include the precise description of the anatomical area, pain duration and limitation level.

Managing informal learning in engineering contexts: the learners' perspective

According to recent studies, informal learning accounts for more than 75% of our continuous learning through life. However, the awareness of this learning, its benefits and its potential is still not very clear. In engineering contexts, informal learning could play an invaluable role helping students or employees to engage with peers and also with more experience colleagues, exchanging ideas and discussing problems. This work presents an initial set of results of the piloting phase of a project (TRAILER) where an innovative service based on Information & Communication Technologies was developed in order to aid the collection and visibility of informal learning. This set of results concerns engineering contexts (academic and business), from the learners' perspective. The major idea that emerged from these piloting trials was that it represented a good way of collecting, recording and sharing informal learning that otherwise could easily be forgotten. Several benefits were reported between the two communities such as being helpful in managing competences and human resources within an institution.

ERICA: prevalence of metabolic syndrome in Brazilian adolescents

ABSTRACT OBJECTIVE To determine the prevalence of metabolic syndrome and its components in Brazilian adolescents. METHODS We evaluated 37,504 adolescents who were participants in the Study of Cardiovascular Risks in Adolescents (ERICA), a cross-sectional, school-based, national study. The adolescents, aged from 12 to 17 years, lived in cities with populations greater than 100,000 inhabitants. The sample was stratified and clustered into schools and classes. The criteria set out by the International Diabetes Federation were used to define metabolic syndrome. Prevalences of metabolic syndrome were estimated according to sex, age group, school type and nutritional status. RESULTS Of the 37,504 adolescents who were evaluated: 50.2% were female; 54.3% were aged from 15 to 17 years, and 73.3% were from public schools. The prevalence of metabolic syndrome was 2.6% (95%CI 2.3-2.9), slightly higher in males and in those aged from 15 to 17 years in most macro-regions. The prevalence was the highest in residents from the South macro-region, in the younger female adolescents and in the older male adolescents. The prevalence was higher in public schools (2.8% [95%CI 2.4-3.2]), when compared with private schools (1.9% [95%CI 1.4-2.4]) and higher in obese adolescents when compared with nonobese ones. The most common combinations of components, referring to 3/4 of combinations, were: enlarged waist circumference (WC), low HDL-cholesterol (HDL-c) and high blood pressure; followed by enlarged WC, low HDL-c and high triglycerides; and enlarged WC, low HDL-c, high triglycerides and blood pressure. Low HDL was the second most frequent component, but the highest prevalence of metabolic syndrome (26.8%) was observed in the presence of high triglycerides. CONCLUSIONS ERICA is the first Brazilian nation-wide study to present the prevalence of metabolic syndrome and describe the role of its components. Despite the prevalence of Metabolic Syndrome being low, the high prevalences of some components and participation of others in the syndrome composition shows the importance of early diagnosis of this changes, even if not grouped within the metabolic syndrome.

Managing Informal Learning in professional contexts: the learner’s perspective

Informal Learning is present in everyone's life but its awareness only recently has been reported. The need to keep track of the knowledge acquired this way is increasing as its sources diversity also increases. This work presents the pilots trials on the use of a tool developed to help keeping track of the learners’ informal learning, within a number of companies spread out in three countries. This tool developed through the European Commission funded project TRAILER, is still under development, which will allow integrating the set of improving suggestions obtained from users during the piloting phase. The overall idea of managing one’s informal learning was well accepted and welcomed, which validated the emerging need for a tool with this purpose.

A tool to aid institutions recognize their employees competences acquired by informal learning

People do not learn only in formal educational institutions, but also throughout their lives, from their experiences, conversations, observations of others, exploration of the Internet, meetings and conferences, and chance encounters etc. However this informal and non-formal learning can easily remain largely invisible, making it hard for peers and employers to recognize or act upon it. The TRAILER project aims to make this learning visible so that it can benefit both the individual and the organization. The proposed demonstration will show a software solution that (i) helps the learners to capture, organize and classify a wide range of ’informal’ learning taking place in their lives, and (ii) assists the organization in recognizing this learning and use it to help managing human resources (benefiting both parts). This software tool has recently been used in two phases of pilot studies, which have run in four different European countries.

Densities and refractive indices for the ternary mixture methanol/propan-1-Ol/acetonitrile

Refractive indices, n(D), and densities, rho, at 298.15 K were measured for the ternary mixture methanol (MeOH)/propan-1-ol (1-PrOH)/acetonitrile (MeCN) for a total of 22 mole fractions, along with 18 mole fractions of each of the corresponding binary mixtures, methanol/propan-1-ol, propan-1-ol/acetonitrile and methanol/acetonitrile. The variation of excess refractive indices and excess molar volumes with composition was modeled by the Redlich-Kister polynomial function in the case of binary mixtures and by the Cibulka equation for the ternary mixture. A thermodynamic approach to excess refractive indices, recently proposed by other authors, was applied for the first time to ternary liquid mixtures. Structural effects were identified and interpreted both in the binary and ternary systems. A complex relationship between excess refractive indices and excess molar volumes was identified, revealing all four possible sign combinations between these two properties. Structuring of the mixtures was also discussed on the basis of partial molar volumes of the binary and ternary mixtures.

Joining models with stair nesting

In the stair nested designs with u factors we have u steps and a(1), ... , a(u) "active" levels. We would have a(1) observations with different levels for the first factor each of them nesting a single level of each of the remaining factors; next a(2) observations with level a(1) + 1 for the first factor and distinct levels for the second factor each nesting a fixed level of each of the remaining factors, and so on. So the number of level combinations is Sigma(u)(i=1) a(i). In meta-analysis joint treatment of different experiments is considered. Joining the corresponding models may be useful to carry out that analysis. In this work we want joining L models with stair nesting.

Single-lap joints of similar and dissimilar adherends bonded with an acrylic adhesive

In this study, the tensile strength of single-lap joints (SLJs) between similar and dissimilar adherends bonded with an acrylic adhesive was evaluated experimentally and numerically. The adherend materials included polyethylene (PE), polypropylene (PP), carbon-epoxy (CFRP), and glass-polyester (GFRP) composites. The following adherend combinations were tested: PE/PE, PE/PP, PE/CFRP, PE/GFRP, PP/PP, CFRP/CFRP, and GFRP/GFRP. One of the objectives of this work was to assess the influence of the adherends stiffness on the strength of the joints since it significantly affects the peel stresses magnitude in the adhesive layer. The experimental results were also used to validate a new mixed-mode cohesive damage model developed to simulate the adhesive layer. Thus, the experimental results were compared with numerical simulations performed in ABAQUS®, including a developed mixed-mode (I+II) cohesive damage model, based on the indirect use of fracture mechanics and implemented within interface finite elements. The cohesive laws present a trapezoidal shape with an increasing stress plateau, to reproduce the behaviour of the ductile adhesive used. A good agreement was found between the experimental and numerical results.

Evaluating the combination of relaxation and argumentation in ontology matching negotiation

No decorrer dos últimos anos, os agentes (inteligentes) de software foram empregues como um método para colmatar as dificuldades associadas com a gestão, partilha e reutilização de um crescente volume de informação, enquanto as ontologias foram utilizadas para modelar essa mesma informação num formato semanticamente explícito e rico. À medida que a popularidade da Web Semântica aumenta e cada vez informação é partilhada sob a forma de ontologias, o problema de integração desta informação amplifica-se. Em semelhante contexto, não é expectável que dois agentes que pretendam cooperar utilizem a mesma ontologia para descrever a sua conceptualização do mundo. Inclusive pode revelar-se necessário que agentes interajam sem terem conhecimento prévio das ontologias utilizadas pelos restantes, sendo necessário que as conciliem em tempo de execução num processo comummente designado por Mapeamento de Ontologias [1]. O processo de mapeamento de ontologias é normalmente oferecido como um serviço aos agentes de negócio, podendo ser requisitado sempre que seja necessário produzir um alinhamento. No entanto, tendo em conta que cada agente tem as suas próprias necessidades e objetivos, assim como a própria natureza subjetiva das ontologias que utilizam, é possível que tenham diferentes interesses relativamente ao processo de alinhamento e que, inclusive, recorram aos serviços de mapeamento que considerem mais convenientes [1]. Diferentes matchers podem produzir resultados distintos e até mesmo contraditórios, criando-se assim conflitos entre os agentes. É necessário que se proceda então a uma tentativa de resolução dos conflitos existentes através de um processo de negociação, de tal forma que os agentes possam chegar a um consenso relativamente às correspondências que devem ser utilizadas na tradução de mensagens a trocar. A resolução de conflitos é considerada uma métrica de grande importância no que diz respeito ao processo de negociação [2]: considera-se que existe uma maior confiança associada a um alinhamento quanto menor o número de conflitos por resolver no processo de negociação que o gerou. Desta forma, um alinhamento com um número elevado de conflitos por resolver apresenta uma confiança menor que o mesmo alinhamento associado a um número elevado de conflitos resolvidos. O processo de negociação para que dois ou mais agentes gerem e concordem com um alinhamento é denominado de Negociação de Mapeamentos de Ontologias. À data existem duas abordagens propostas na literatura: (i) baseadas em Argumentação (e.g. [3] [4]) e (ii) baseadas em Relaxamento [5] [6]. Cada uma das propostas expostas apresenta um número de vantagens e limitações. Foram propostas várias formas de combinação das duas técnicas [2], com o objetivo de beneficiar das vantagens oferecidas e colmatar as suas limitações. No entanto, à data, não são conhecidas experiências documentadas que possam provar tal afirmação e, como tal, não é possível atestar que tais combinações tragam, de facto, o benefício que pretendem. O trabalho aqui apresentado pretende providenciar tais experiências e verificar se a afirmação de melhorias em relação aos resultados das técnicas individuais se mantém. Com o objetivo de permitir a combinação e de colmatar as falhas identificadas, foi proposta uma nova abordagem baseada em Relaxamento, que é posteriormente combinada com as abordagens baseadas em Argumentação. Os seus resultados, juntamente com os da combinação, são aqui apresentados e discutidos, sendo possível identificar diferenças nos resultados gerados por combinações diferentes e possíveis contextos de utilização.

Incorporating sustainability into a chemical company’s modus operandi

The intent of this dissertation is to review relevant existing management systems and chemical industry initiatives to identify synergies, overlaps and gaps with Sustainability best practices, to map the barriers to the incorporation of Sustainability and formulate recommendations to facilitate execution of Sustainability practices within existing management systems. A chemical industry Sustainability survey was conducted through APEQ, the Portuguese association of chemical companies, which constitutes the first baseline on the topic for this national industry association. The commonly used international standards and the Responsible Care® (RC) initiative were cross-referenced against the United Nations Global Compact Assessment Tool. Guidance on how to incorporate Sustainability into a company‘s modus operandi was collapsed into Sustainability Playbooks. The survey revealed that 73% of the APEQ member companies that participated in the survey have a Sustainability Plan. Both large and small/medium APEQ member companies see the market not willing to pay extra for ‗greener‘ products as one of the main barriers. APEQ large enterprise see complexity of implementation and low return on investment as the other most significant barriers while small/medium enterprise respond that the difficulty to predict customer sustainability needs is the other most significant barrier. Amongst many other insights from this survey reported to APEQ, Life Cycle Assessment practices were found to have a low level of implementation and were also considered of low importance, thus identifying a very important opportunity in Sustainability practices to be addressed by APEQ. Two hundred and seventy three assessment points from United Nations Global Compact Assessment Tool plus five additional items were cross-referenced with international standard requirements. With the authorization of the intellectual property owners, the United Nations Global Compact Assessment Tool was modified to introduce actionable recommendations for each gap identified by management standard. This tool was automated to output specific recommendations for 63 possible combinations after simply selecting from a list of commonly used management standards and the RC initiative. Finally this modified tool was introduced into Playbooks for Incorporation of Sustainability at two levels: a ―Get Started Playbook‖ for beginners or small/medium size enterprise and an ―Advanced Playbook‖ as a second advancement stage or for large enterprise.

A pré-fabricação em betão em edifícios

No presente trabalho apresenta-se um levantamento com base na literatura especializada, das diversas soluções estruturais em betão pré-fabricado existentes, aplicadas em edifícios correntes, mais especificamente as soluções ao nível dos elementos que as constituem, nomeadamente no que respeita a ligações estruturais dos elementos, com combinações in situ, das estruturas préfabricadas e as moldadas em obra, aproveitando o que de melhor se pode obter de ambas as técnicas, com vista a obter um melhor resultado final. Apesar do setor da construção civil estar em crise, tal como vários outros setores, as empresas de pré-fabricação apresentam soluções que poderão contrariar esta tendência, nomeadamente através da diversificação e flexibilização da sua produção, com inovação, criatividade e elevada qualidade. Num mercado em que a construção de edifícios de raiz sofreu um grande abrandamento, começa a surgir no mercado a necessidade de se reabilitar as construções existentes, nomeadamente nos grandes centros das cidades que foram perdendo população ao longo dos tempos. Esta requalificação do espaço urbano permite o desenvolvimento de soluções estruturais pré-fabricadas, no que respeita à reabilitação dos elementos existentes, quer por justaposição para reforço das estruturas, quer por inserção de elementos novos para efetuar correções. Os baixos custos de mão de obra, equipamentos e estaleiro, assim como a redução dos prazos de construção e entrega ao cliente final, dado que a produção não está dependente das condições existentes in situ para se desenvolver, destacam-se da construção civil tradicional. A produção integral dos elementos pré-fabricados de betão em fábrica tem outras vantagens, entre as quais, um melhor planeamento e controle da segurança, um controle rigoroso de qualidade, a redução dos custos de reparação e manutenção, melhor sustentabilidade com redução da quantidade de resíduos produzidos.

A Lei de ZIPF ou Regra 80/20 da Internet

As Leis de Potência, LP, (Power Laws, em inglês), Leis de Pareto ou Leis de Zipf são distribuições estatísticas, com inúmeras aplicações práticas, em sistemas naturais e artificiais. Alguns exemplos são a variação dos rendimentos pessoais ou de empresas, a ocorrência de palavras em textos, as repetições de sons ou conjuntos de sons em composições musicais, o número de vítimas em guerras ou outros cataclismos, a magnitude de tremores de terra, o número de vendas de livros ou CD’s na internet, o número de sítios mais acedidos na Internet, entre muitos outros. Vilfredo Pareto (1897-1906) afirma, no manual de economia política “Cours d’Economie Politique”, que grande parte da economia mundial segue uma determinada distribuição, em que 20% da população reúne 80% da riqueza total do país, estando, assim uma pequena fração da sociedade a controlar a maior fatia do dinheiro. Isto resume o comportamento de uma variável que segue uma distribuição de Pareto (ou Lei de Potência). Neste trabalho pretende-se estudar em pormenor a aplicação das leis de potência a fenómenos da internet, como sendo o número de sítios mais visitados, o número de links existentes em determinado sítio, a distribuição de nós numa rede da internet, o número livros vendidos e as vendas em leilões online. Os resultados obtidos permitem-nos concluir que todos os dados estudados são bem aproximados, numa escala logarítmica, por uma reta com declive negativo, seguindo, assim, uma distribuição de Pareto. O desenvolvimento e crescimento da Web, tem proporcionado um aumento do número dos utilizadores, conteúdos e dos sítios. Grande parte dos exemplos presentes neste trabalho serão alvo de novos estudos e de novas conclusões. O fato da internet ter um papel preponderante nas sociedades modernas, faz com que esteja em constante evolução e cada vez mais seja possível apresentar fenómenos na internet associados Lei de Potência.

Análise estocástica com recurso a ferramentas informáticas no planeamento de empreitadas de construção

O presente trabalho, desenvolvido sob a orientação do Prof. Jaime Gabriel Silva, centra-se na procura e aplicação de metodologias de planeamento com apoio de ferramentas informáticas de análise de risco, que permitem realizar, em tempo útil, o cálculo dos prazos resultantes de inúmeras combinações possíveis associadas à incerteza das durações das atividades, recorrendo a modelos estocásticos. O trabalho aborda inicialmente o contexto da Gestão na Construção, com particular enfase na Gestão do Risco. Nessa fase inicial, fez-se também um pequeno inquérito a profissionais com diferentes níveis de responsabilidade organizacional e empresas do setor. A parte fundamental do trabalho, incide nos procedimentos a adotar na elaboração do planeamento de empreitadas. Nesta parte do trabalho, introduzem-se os conceitos da análise de risco com recurso a uma ferramenta informática de apoio, o @Risk, que permite a utilização do Método de Monte Carlo, para obtenção de resultados num contexto de uma tomada de decisão baseada no risco. Refira-se que houve vários contactos com o fornecedor do programa, que permitiram tirar partido de outro programa da Palisade, Evolver, direcionado para otimização matemática, podendo ser utilizado, por exemplo, na perspetiva da minimização dos custos, o que pode interessar pela relação destes com as opções adotadas na elaboração do planeamento de empreendimentos. Finalmente, toma-se um exemplo real do planeamento de uma empreitada em execução à data da realização deste trabalho, onde se aplicaram os conceitos desenvolvidos no trabalho, confrontando os resultados com o andamento da obra.