Browsing by Issue Date, starting with "2016-11"
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- Modelação numérica do escorregamento de armaduras em elementos de betão armadoPublication . Sousa, Romain; Correia, António A.; Almeida, João P.; Pinho, RuiEstruturas porticadas de betão armado (BA) sujeitas à ação sísmica apresentam frequentemente deformações localizadas nas extremidades dos seus elementos devidas ao escorregamento das armaduras em relação ao betão, nomeadamente ao longo do seu comprimento de amarração. Apesar de as mesmas poderem representar 40% da deformação lateral total de elementos em BA, a modelação numérica deste comportamento apresenta ainda diversas limitações. O presente artigo introduz uma estratégia de simulação onde, pela primeira vez, um modelo explícito para o escorregamento de armaduras é associado a um elemento de viga, com discretização seccional por fibras, através de um elemento de ligação com comprimento nulo. O elemento proposto adota uma sofisticada relação constitutiva de aderência, representando os efeitos da degradação cíclica ou da cedência das armaduras, entre outros. O modelo é validado através da comparação entre resultados numéricos e experimentais, demonstrando uma eficiência, precisão e estabilidade numérica assinaláveis.
- A importância do Profissional de Secretariado na Performance das EmpresasPublication . Nogueira, Marta; Santos, Tânia Cristina Simões de Matos dos; Sousa, MarleneO ambiente empresarial tem sofrido nas últimas décadas profundas e constantes alterações, onde as tecnologias da informação, a formação de grupos económicos e a crise internacional impõem novos desafios. Neste sentido, é imperativo dotar as organizações de equipas multidisciplinares, competentes, empreendedoras e eficientes. Por outro lado, o papel do profissional de secretariado tem evoluído com estas alterações, tornando-se cada vez mais importante e imprescindível para a boa performance das empresas. Nos dias de hoje, os profissionais de secretariado assumem regularmente uma posição estratégica nas organizações, possuem uma visão generalista e sistémica do processo organizacional e da sua cultura, atuam como consultores e assessores e participam ativamente ao lado do poder decisório das organizações. A importância do profissional de secretariado permanece, ainda assim, pouco reconhecida no interior das organizações e pelo próprio mercado de trabalho, que desconhecem a mudança de paradigma desta profissão e continuam a visualizar o papel do secretariado nas organizações como o assumido há várias décadas atrás. A investigação proposta tem como objetivo perceber se os diplomados de cursos ligados à área do secretariado, e que cumulativamente realizaram estágio curricular nesta área, compreenderam a importância da sua função na performance das organizações e investigar quais as competências que identificam como cruciais no perfil do profissional de secretariado.
- Improvement in fatigue life of Al 7475-T7351 alloy specimens by applying ultrasonic and microshot peeningPublication . Ramos, R.; Ferreira, N.; Ferreira, J.A.M.; Capela, Carlos; Batista, A.C.Shot peening and ultrasonic peening are widely used mechanical surface treatment in the automotive and aerospace industries to improve the fatigue life of metallic components. This work aims to further improve the mechanical properties of the AA7475-T7351 alloy by applying three different peening processes: Ultrasonic Peening (USP) and Microshot Peening with two different beads size (MSP). A systematic study was carried out on the roughness, surface hardening, residual stress profiles and fatigue life. Uniaxial fatigue tests were conducted. Residual stresses were evaluated by X-ray diffraction, and the fracture surface was observed and analysed with a Scanning Electron Microscope. The microstructures of the specimens were observed by optic microscope. Microhardness and roughness were also measured. All of the surface treatments enhanced the specimens fatigue lives, despite having created different superficial conditions. In addition, the experimental results and analytic predictions based on the Molski-Glinka approach were compared, and in general, agree well.
- A spam filtering multi-objective optimization study covering parsimony maximization and three-way classificationPublication . Basto-Fernandes, Vitor; Yevseyeva, Iryna; Méndez, José R.; Zhao, Jiaqi; Fdez-Riverola, Florentino; Emmerich, Michael T.M.Classifier performance optimization in machine learning can be stated as a multi-objective optimization problem. In this context, recent works have shown the utility of simple evolutionary multi-objective algorithms (NSGA-II, SPEA2) to conveniently optimize the global performance of different anti-spam filters. The present work extends existing contributions in the spam filtering domain by using three novel indicator-based (SMS-EMOA, CH-EMOA) and decomposition-based (MOEA/D) evolutionary multiobjective algorithms. The proposed approaches are used to optimize the performance of a heterogeneous ensemble of classifiers into two different but complementary scenarios: parsimony maximization and e-mail classification under low confidence level. Experimental results using a publicly available standard corpus allowed us to identify interesting conclusions regarding both the utility of rule-based classification filters and the appropriateness of a three-way classification system in the spam filtering domain.
- Multiobjective optimization of classifiers by means of 3D convex-hull-based evolutionary algorithmsPublication . Zhao, Jiaqi; Basto-Fernandes, Vitor; Jiao, Licheng; Yevseyeva, Iryna; Maulana, Asep; Li, Rui; Bäck, Thomas; Tang, Ke; Emmerich, Michael T.M.The receiver operating characteristic (ROC) and detection error tradeoff (DET) curves are frequently used in the machine learning community to analyze the performance of binary classifiers. Recently, the convex-hull-based multiobjective genetic programming algorithm was proposed and successfully applied to maximize the convex hull area for binary classification problems by minimizing false positive rate and maximizing true positive rate at the same time using indicator-based evolutionary algorithms. The area under the ROC curve was used for the performance assessment and to guide the search. Here we extend this research and propose two major advancements: Firstly we formulate the algorithm in detection error tradeoff space, minimizing false positives and false negatives, with the advantage that misclassification cost tradeoff can be assessed directly. Secondly, we add complexity as an objective function, which gives rise to a 3D objective space (as opposed to a 2D previous ROC space). A domain specific performance indicator for 3D Pareto front approximations, the volume above DET surface, is introduced, and used to guide the indicator-based evolutionary algorithm to find optimal approximation sets. We assess the performance of the new algorithm on designed theoretical problems with different geometries of Pareto fronts and DET surfaces, and two application-oriented benchmarks: (1) Designing spam filters with low numbers of false rejects, false accepts, and low computational cost using rule ensembles, and (2) finding sparse neural networks for binary classification of test data from the UCI machine learning benchmark. The results show a high performance of the new algorithm as compared to conventional methods for multicriteria optimization.
- Non-lethal heat shock increases tolerance to metal exposure in brine shrimpPublication . Pestana, João L.T.; Novais, Sara; Norouzitallab, Parisa; Vandegehuchte, Michiel B.; Bossier, Peter; De Schamphelaere, Karel A.C.Pollution and temperature increase are two of the most important stressors that aquatic organisms are facing. Exposure to elevated temperatures and metal contamination both induce heat shock proteins (HSPs), which may thus be involved in the induced cross-tolerance in various organisms. This study aimed to test the hypothesis that exposure to a non-lethal heat shock (NLHS) causes an increased tolerance to subsequent metal exposure. Using gnotobiotic cultures of the brine shrimp Artemia franciscana, the tolerance to Cd and Zn acute exposures was tested after a prior NLHS treatment (30 min exposure to 37 °C). The effects of NLHS and metal exposure were also assessed by measuring 70 kDa-HSPs production, along with the analysis of epigenetic markers such as DNA methylation and histone H3 and histone H4 acetylation. Our results showed that heat-shocked Artemia had increased acute tolerance to Cd and Zn. However, different patterns of HSPs were observed between the two metal compounds and no epigenetic alterations were observed in response to heat shock or metal exposure. These results suggest that HSP production is a phenotypically plastic trait with a potential role in temperature-induced tolerance to metal exposure.
- Export performance as a function of market learning capabilities and intrapreneurship: SEM and FsQCA findingsPublication . Skarmeas, Dionysis; Lisboa, Ana; Saridakis, CharalamposThis study draws on the resource-based, dynamic capabilities, and organization learning theories to investigate the internal mechanisms through which intrapreneurship influences current and future export performance. Specifically, this approach views the four distinct dimensions of intrapreneurship, namely new business venturing, innovativeness, self-renewal, and proactiveness, as critical resources, and export market exploitation and exploration as important market learning capabilities. The study posits that such resources and capabilities collectively contribute to improve export performance outcomes. The study develops a theoretically anchored model and employs both structural equation modeling and fuzzy-set qualitative comparative analysis to test the model relationships. These two techniques have different foci: the net effect of an independent variable on an outcome variable and the conditions that lead to a given outcome, respectively. The study results provide substantial support for the theoretical framework and a valuable addition to the scant literature on the roles of intrapreneurship and market exploitation and exploration in exporting.
- Biomechanically Inspired Shape Memory Effect Machines Driven by Muscle like Acting NiTi AlloysPublication . Raffaella Aversa; Francesco Tamburrino; Relly Victoria V. Petrescu; Florian Ion T. Petrescu; Mateus, Artur; Guanying, Chen; Antonio ApicellaThe research shows a bioinspired approach to be adopted to design of systems based on Shape Memory Alloys (SMAs), a class of Smart Materials that has in common with muscles the capability to react to an impulse (thermal for SMAs) with a contraction. The biomechanically inspired machine that is discussed in the paper refers to the antagonistic muscles pairs, which belongs to the Skeletal Muscles and are normally arranged in opposition so that as one group of muscles contract another group relaxes or lengthens. The study proposes a model, a solution not only to design a specific application, but also to provide an approach to be used for a wide range of adaptive applications (switchable windows, smart shadow systems, parking and urban shelters, etc.), where the shape changes in response to different external stimuli. The use of antagonist pairs mechanism provides a solution for better optimized systems based on SMAs where the main and proven advantages are: Easier and faster change of shape, lower need of energy for system operation, lower cost for SMA training and no problem of overheating.
- The effects of celebrity endorsement on the consumers’ perceptions towards global brandsPublication . Popa, Victor; Crespo, Cátia Claudemira Cordeiro FernandesBrands are those lifestyles which consumers chose to buy in order to gain the value offered by the company, in order to be part of the community created through the brand equity elements and validated in the purchase of the products. Companies have understood how important it is to build a strong brand and many of them spend millions on aligning the brand with the design and style of the products, projecting the face and values of the company into the advertising campaigns. One of the most popular methods is through endorsement, placing a renounced celebrity and leveraging on the positive feedback of those customers that also follow the activities of the star whose face is on the cover of the marcom campaign. Celebrities have been used for a very long time to promote brands, sell products and services. Research has shown that those spokesmen of a brand who are more attractive can improve the statistics of recall and appeal more interest to the promotion campaign, as well as influence more on customer’s intention of buying the product (Kahle and Homer, 1985). The main purpose of this research is to investigate how celebrity endorsements influence the brand equity dimensions (brand loyalty, brand awareness, perceived quality and brand associations) as well as stimulate consumers’ word-of-mouth through brand identification, growth in interest and the advertising memorability. The hypotheses were tested with the aid of Structural Equation Modelling (SEM) in the PLS (Partial Least Squares) software. The survey is comprised of a target group of 589 respondents, from three countries – Brazil, Moldova and Portugal. Results evidence that the Attitude towards the Celebrity influences different Brand Equity dimensions and affects brand identification, growth in advertisement interest and advertising memorability, generating positive word of mouth (or negative, depending on the type of advertisement and reputation). Based on these findings we suggest further investigation in this area with the possibility to gain more data about the different fields of marcom and the different types of CE which are more appropriate for the given type of business.
- Participation of portuguese manufacturing industry in global value chainsPublication . Pechankova, Katsiaryna; Sargento, Ana Lúcia MartoPortugal’s manufacturing sector has a significant importance both in national income and employment. As has been pointed out by several researchers, the traditional methods of analysis fail to grasp all the dimensions of economic competitiveness. This dissertation is then, at its core, an analysis of Portugal’s manufacturing industry in terms of the latter’s value added to production and impact to employment under the framework of global value chains. The current dissertation seeks to study in which way the Portuguese manufacturing industry, and its respective sectors, has a direct and indirect impact on the creation of value added and employment and how this impact can be measured. For development of this work the input-output approach for calculation of multipliers and the new framework proposed by Timmer et al. (2013) for calculation of GVC income and GVC jobs indicators were used, elaborated on the basis of the WIOD project dataset. Moreover, to illustrate the application of the provided methodology the Portuguese textile industry was used as an example. It was found that the changes in final demand of such sectors as Pulp, Paper, Printing and Publishing; Machinery, Nec and Textiles and Textile Products would have a larger impact on generated value added than other manufacturing sectors. At the same time, employment created by the changes in final demand would be more impacted by such sectors as Food, Beverages and Tobacco; Wood and Products of Wood and Cork and Textiles and Textile Products. In this regard, the number of low-skilled workers in Portugal seems to be more effected by changes in final demand, than those occupied by higher -skilled individuals. Moreover, it was found that the distribution of GVC income and GVC jobs for the Portuguese manufacturing industry shares a similar outlook. However, upon closer inspection of GVC labour distribution by skill levels there seems to exist a general progression in which low-skilled jobs requirements are met by local resources, while the need for higher skilled jobs require a greater “off-shoring” of work The results obtained through calculations of presented multipliers provide a powerful tool for policy makers in strategic planning of development of national economy. Using the provided methodology and obtained results, a government and supranational organizations could define which industry would have the greatest impact for an additional unit of output generated through the economy, and thus define the sectors for further investments.