Nonlocal free vibrations of metallic FGM beams

This work aims to analyse the free-vibration response of functionally graded, simply supported beams with different gradient directions, taking into account nonlocal effects. To this purpose, the first-order shear deformation theory and the nonlocal elasticity theory of Eringen are used, in order to assess the influence of size dependency effects on the free-vibration responses of those beams. The influence of other factors such as the aspect ratio of the beams and the evolution of the constituents’ mixture through the beam thickness and along its length is also considered. In this last case, a mixture distribution is proposed, accounting for the boundary conditions’ characteristics. The finite element model is first verified against existing alternative solutions, to assess and illustrate its performance. Based on the conclusions achieved, a set of parametric studies is then developed. The results are discussed considering the material distribution profiles, and conclusions are drawn with respect to their relative performance under the analysed conditions.info:eu-repo/semantics/publishedVersio

3D printing of abdominal immobilization masks for therapeutics: dosimetric, mechanical and financial analysis

Molding immobilization masks is a time-consuming process, strongly dependent on the healthcare professional, and potentially uncomfortable for the patient. Thus, an alternative sustainable automated production process is proposed for abdominal masks, using fused deposition modelling (FDM) 3D printing with polylactic acid (PLA). Radiological properties of PLA were evaluated by submitting a set of PLA plates to photon beam radiation, while estimations of their mechanical characteristics were assessed through numerical simulation. Based on the obtained results, the abdominal mask was 3D printed and process costs and times were analyzed. The plates revealed dose transmissions similar to the conventional mask at all energies, and mechanical deformation guarantees the required immobilization, with a 66% final cost reduction. PLA proved to be an excellent material for this purpose. Despite the increase in labour costs, a significant reduction in material costs is observed with the proposed process. However, the time results are not favorable, mainly due to the printing technique used in this study.info:eu-repo/semantics/publishedVersio

A study on the effect of carbon nanotubes’ distribution and agglomeration in the free vibration of nanocomposite plates

The present work aimed to characterize the free vibrations’ behaviour of nanocomposite plates obtained by incorporating graded distributions of carbon nanotubes (CNTs) in a polymeric matrix, considering the carbon nanotubes’ agglomeration effect. This effect is known to degrade material properties, therefore being important to predict the consequences it may bring to structures’ mechanical performance. To this purpose, the elastic properties’ estimation is performed according to the two-parameter agglomeration model based on the Eshelby–Mori–Tanaka approach for randomly dispersed nano-inclusions. This approach is implemented in association with the finite element method to determine the natural frequencies and corresponding mode shapes. Three main agglomeration cases were considered, namely, agglomeration absence, complete agglomeration, and partial agglomeration. The results show that the agglomeration effect has a negative impact on the natural frequencies of the plates, regardless the CNTs’ distribution considered. For the corresponding vibrations’ mode shapes, the agglomeration effect was shown in most cases not to have a significant impact, except for two of the cases studied: for a square plate and a rectangular plate with symmetrical and unsymmetrical CNTs’ distribution, respectively. Globally, the results confirm that not accounting for the nanotubes’ agglomeration effect may lead to less accurate elastic properties and less structures’ performance predictions.info:eu-repo/semantics/publishedVersio

Static and Free Vibration Analyses of Functionally Graded Plane Structures

In recent years, the use of functionally graded materials has been the focus of several studies due to their intrinsic ability to be tailored according to the requirements of structures while minimising abrupt stress transitions commonly found in laminated composites. In most studies, the materials’ mixture gradient is established through a structural component, i.e., thickness, which is known to visibly enhance structural behaviour. However, depending on the type of structure, it is important to exploit the possibility of building a structure using other gradient directions. The innovative characteristic of this work, which aims to study plane truss and frame-type structures made of functionally graded materials, lies in the specificity that the materials’ mixture gradient occurs as a function of a geometric structure feature, i.e., for example, the structure height, rather than the more usual approach, as a component dependence, i.e., through a member thickness or even along its length. The performance of the present model is illustrated through a set of case studies, and where possible, the results achieved are compared with more traditional solutions

2019 world of shipping Portugal. An international research conference on maritime affairs editorial “Leading the shipping industry into the future”

Background, the context and purpose of the study: The current Editorial addresses the evolutionary path of the shipping industry. It mentions its role throughout the years, identifies the leading market segments, refers to the different operational modes due to the inherent nature of the cargoes they carry and lists some trends that appear to have been shaping the maritime industry. Within the scope of this background, the Editorial claims that all maritime market segments face the same future challenges and lists a range of international legislation released by the International Maritime Organisation which industry players must comply with. Findings, the main results: Not/aplicable. Conclusions, brief summary and potential implications: The Editorial concludes by stating that the maritime industry will benefit from the implementation of innovative solutions and further claims that wrong decisions will have severe impacts on the finances of the shipping companies and the environment. Moreover, it presents in a brief way the papers published in this Special Issue, which were selected among the ones presented at the 2019 World of Shipping Portugal, an International Research Conference on Maritime Affairs, 21–22 November 2019, that took place at Hotel Riviera, in Carcavelos, Portugal.info:eu-repo/semantics/publishedVersio

2021 World of shipping Portugal: an international research conference on maritime afairs editorial

Currently, the shipping industry is at a crossroads. Although it has overcome numerous technological barriers and fnance and economic crises over the years, the industry is facing its most prominent challenge, which rests on fnding the most feasible solutions to deal with industry decarbonisation until 2050. Within this scope, the current Editorial addresses the issue of sulphur emissions that the industry faced with the entrance of the sulphur regulation on 1 January 2020 and draws attention to the road that the industry players need to cover to decarbonise the shipping industry. Innovative measures like the Poseidon Principles or the Sea Cargo Charter are in place, and industry players are coming together to fnd feasible solutions. Within this regulatory environment, the shipping industry also had to deal with the COVID-19 Pandemic. However, some market segments, such as the container and dry bulk ones, have managed to survive, which is not the case with the tanker market. Altogether, these events draw the industry to deal with the market, technology, and regulatory challenges and risks whose outcome is yet to be seen. The Editorial concludes by presenting briefy the papers published in this Special Issue, which were selected among the ones presented at the 2021 World of Shipping Portugal, an international research conference on maritime afairs, 28–29 January 2021, that took place online from Portugal to the World due to the Covid-19 pandemic.info:eu-repo/semantics/publishedVersio

Toward variability characterization and statistic models' constitution for the prediction of exponentially graded plates' static response

Functionally graded composite materials may constitute an advantageous alternative to engineering applications, allying a customized tailoring capability to its inherent continuous properties transition. However, these attractive characteristics must account for the uncertainty that affects these materials and their structures' physical quantities. Therefore, it is important to analyze how this uncertainty will modify the foreseen deterministic response of a structure that is built with these materials, identifying which of the parameters are responsible for a greater impact. To pursue this main objective, the material and geometrical parameters that characterize a plate made of an exponentially graded material are generated according to a random multivariate normal distribution, using the Latin hypercube sampling technique. Then, a set of finite element analyses based on the first-order shear deformation theory are performed to characterize the linear static responses of these plates, which are further correlated to the input parameters. This work also considers the constitution of statistic models in order to allow their use as alternative prediction models. The results show that for the plates that were analyzed, the uncertainty associated with the elasticity modulus of both phases is mainly responsible for the maximum transverse deflection variability. The effectiveness of the statistical models that are built are also shown.info:eu-repo/semantics/publishedVersio

Variable stiffness composites: optimal design studies

Este trabalho foi financiado pelo Concurso Anual para Projetos de Investigação, Desenvolvimento, Inovação e Criação Artística (IDI&CA) 2016 do Instituto Politécnico de Lisboa. Código de referência IPL/2019/MOCHVar_ISELThis research work has two main objectives, being the first related to the characterization of variable stiffness composite plates’ behavior by carrying out a comprehensive set of analyses. The second objective aims at obtaining the optimal fiber paths, hence the characteristic angles associated to its definition, that yield maximum fundamental frequencies, maximum critical buckling loads, or minimum transverse deflections, both for a single ply and for a three-ply variable stiffness composite. To these purposes one considered the use of the first order shear deformation theory in connection to an adaptive single objective method. From the optimization studies performed it was possible to conclude that significant behavior improvements may be achieved by using variable stiffness composites. Hence, for simply supported three-ply laminates which were the cases where a major impact can be observed, it was possible to obtain a maximum transverse deflection decrease of 11.26%, a fundamental frequency increase of 5.61%, and a buckling load increase of 51.13% and 58.01% for the uniaxial and biaxial load respectively.info:eu-repo/semantics/publishedVersio

Special Focus on Advances in Symbolic and Numeric Computation IV

This Special Focus on Advances in Symbolic and Numeric Computation IV of Mathematics in Computer Science (MCS) edited by Amélia Loja, Mourad Bezzeghoud, Joaquim Infante Barbosa and José Alberto Rodrigues is organized in connection with the 5th International Conference on Numerical and Symbolic Computation: Developments and Applications, and it is devoted to publishing relevant results on the development and/or applications of numerical and symbolic computational methods in Mathematics, Applied Sciences and Engineering. Original research papers and insightful survey manuscripts addressing all aspects of numerical and symbolic computation are welcome. Topics and areas of interest for this special focus include, but are not limited to - integrated numerical and/or symbolic computation, - integrated graphical and/or analytical computation, - image processing, - symbolic computation and didactical tools, - modeling and optimization, - systems identification and control, - evolutionary algorithms, - computational intelligence, - fuzzy systems, - computational mathematics, - computational engineering, - computational physics and chemistry, - computational economics, management and planning, - health and biomedical computing applications, - design and implementation of algorithms and software tools.SYMCOMP202

An optimization strategy for customized radiotherapy head immobilization masks

Project IPL/2016/SoftImob/ISEL. Support of FCT through IDMEC, LAETA, project UID/EMS/50022/2019.An effective head immobilization is an important requirement in radiotherapy treatment sessions, although it may also be thought in the future as a precious aid in brain medical imaging. Thus, the present work is focused on the stiffness optimization of a customized head immobilization mask, modeled upon the head reconstruction surface based on computerized tomography images. This paper proposes a strategy supported by a metaheuristic optimization technique and a metamodeling approach for the whole mask, illustrated at its most unfavorable region occurring in the gnathion region.info:eu-repo/semantics/publishedVersio