ESTGV - DI - Artigo em ata de evento científico internacional
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- Vibração Em Regime Livre de Placas Laminadas Espessas pelo Método dos Elementos Finitos Hierárquico (Free-State Vibration of Thick Rolled Plates using the Hierarchical Finite Element Method)Publication . P. Duarte, Rui; Ribeiro, PedroUm elemento finito hierárquico é desenvolvido para estudar o comportamento não linear geométrico de placas laminadas simétricas e assimétricas em materiais compósitos. É aplicada a teoria de Mindlin e as relações não lineares de von Kármán entre as deformações e os deslocamentos, ou seja, são considerados os efeitos da inércia rotacional, das deformações transversas e da não linearidade geométrica devida a grandes deformações. As equações de movimento no domínio do tempo são determinadas aplicando os princípios dos trabalhos virtuais e de d´Alembert. O modelo é aplicado em regime linear calculando as frequências naturais de placas encastradas, estudando a variação das frequências naturais com a espessura das placas e as propriedades de convergência do elemento. O modelo é validado comparando os resultados com os de outros autores. Já em regime não-linear, as equações são transformadas para o domínio da frequência utilizando o método do balanceamento dos harmónicos e a variação da frequência natural de vibração com a amplitude do deslocamento é analisada.
- Time Domain Analysis of Geometrically Nonlinear Vibrations of Composite Laminated Plates by the Hierarchical Finite Element MethodPublication . P. Duarte, Rui; Ribeiro, P.Composite laminated plates are employed in many areas of engineering such as aeronautics, space engineering and naval industry [1,2,3]. For example in aircrafts they are submitted to large acoustic, aerodynamic and inertia excitations and therefore experience vibrations with large amplitude, i.e., in the geometrically nonlinear regime. Vibrations with large amplitude cause large stresses and the diminution of life due to fatigue. Quasi periodic and chaotic behaviours are other possible consequences of non-linearity, completely ignored by the linear models which are normally used in engineering design. Non-symmetrical laminated plates have been rarely studied, particularly in non-linear dynamics. In this work, a hierarchical finite element, in which the model is improved by increasing the number of shape functions in each element, is formulated. The element is general, in the sense that it applies to symmetric or asymmetric plates. Compared with h-version elements, it has the major advantages of requiring a small number of degrees of freedom for accuracy and of being free from shear locking. Different shear deformation theories (SDT) have been developed to include the effect of transverse shear deformation [1,2,3]. The first order shear deformation laminated plate theory is followed here. Hence, Kirchhoff's hypothesis [4] is relaxed by removing the third part, that is the transverse normals do not remain perpendicular to the mid-surface after deformation. 1 2 3 4 5 6 7 8 9 In this paper, the shape functions used are the Legendre polynomials in the Rodrigue's form [5,6,7,8,9]. A different number of transverse, middle plane, rotation about y and rotation about x, displacement shape functions are employed, and the convergence of the linear natural frequencies studied. Two symmetric, rectangular, graphite/epoxy composite laminated plates with constant thickness , width and length , composed of orthotropic layers oriented at different angles are considered. The element derived is employed to study the non-linear dynamic behaviour of some these laminated plates, in the time domain. The direct integration of the system of equations of motion is carried out by Newmark's method. In order to uncover the characteristics of the motions computed, time plots, phase planes and Fourier spectra are defined. For different fibre orientations, it is confirmed that the linear natural frequencies of the thick plate model are smaller than the thin plate ones. Harmonic excitations are applied, and the responses of the plates are determined with a reasonable computational cost, due to the reduced number of degrees of freedom of the model. For amplitudes of vibration much lower than the thickness of the plate, the solutions found are always periodic and highly dominated by the harmonic with frequency equal to the excitation frequency (principal harmonic). Increasing the force applied, the response amplitude increased in a non-linear way, the motions found are still periodic, but the time and phase plots show that higher harmonics are important.
- Contacts Manager: A Mobile Web Application Consumer of Web ServicesPublication . Sousa, Artur; Wanzeller, Cristina; P. Duarte, Rui; Batista, Manuel; Soares, António; Fernandes, CarlosWith the constant innovations in the mobile devices domain, the need to make available new forms of applications is growing. We believe that this kind of devices may become large consumers of web services. Therefore, we aim to explore the development of applications for mobile devices based in web services. Our project involves the implementation of an application which allows the WAP access to the Intranet/Extranet of an information technologies company, aiming to obtain the information about its costumers, from anywhere.
- Topics on XML Data Storage and ManagementPublication . Sousa, Artur; P. Duarte, Rui; Pereira, José Luís; Carvalho, João ÁlvaroAs new standards for technology specifications related to XML are unveiled, and stable tools to implement them become available, the widespread usage of XML as an universal format for data exchange between heterogeneous e-business systems will increasingly become a reality. In this paper we analyze the several approaches available for the storage and management of XML data.
- An evolved security architecture for distributed industrial automation and control systemsPublication . Rosa, L.; Proença, J.; Henriques, João; Graveto, V.; Cruz, T.; Simões, P.; Caldeira, Filipe; Monteiro, E.Over the recent years, control and sensor systems used for IACS (Industrial Automation and Control Systems) have become more complex, due to the increasing number of interconnected distributed devices, sensors and actuators. Such components are often widely dispersed in the field – this is the case for microgeneration (wire-to-water generation, solar or wind), smart metering, oil and gas distribution or smart water management, among others. This IoT (Internet of Things)-centric IACS paradigm expands the infrastructure boundaries well beyond the single or aggregated-plant, mono-operator vision (mostly associated with geographically constrained systems topologies), being dispersed over a large geographic area, with increasingly small areas of coverage as we progress towards its periphery. This situation calls for a different approach to cyber threat detection, which is one of the most relevant contributions of the ATENA (Advanced Tools to assEss and mitigate the criticality of ICT components and their dependencies over critical infrAstructures) H2020 project (ATENA 2016). This paper presents and describes the ATENA cyber-security architecture, designed for the emerging generation of distributed IoT IACS, leveraging technologies such as Software Defined Networking/Network Function Virtualization and Big data event processing) within the scope of a cyber-detection architecture designed to deal with the inherent challenges of dispersed IACS, involved different operator domains.
- Real-time simulation of cumulus clouds through SkewT/LogP diagramsPublication . P. Duarte, Rui; Gomes, A.J.P.Modeling, simulation, and realistic rendering of natural phenomena have been important goals in computer graphics for decades. Clouds, as a natural phenomenon, represent a real challenge because their birth, life, and death are amorphous and dynamic in nature. As a consequence, cloud simulation is very time-consuming when using physically-based methods. This paper presents a real-time cloud simulation method based on SkewT/LogP diagrams to overcome this time performance problem. These diagrams allow us to simulate 3D clouds from sounding data made public worldwide by weather agencies. More specifically, a SkewT/LogP diagram describes the vertical motion of a cloud in the atmosphere, i.e., our cloud simulator system is based on physics but avoids solving differential equations of cloud motion to achieve real-time rates. We have also built a visual tool for 2D SkewT/LogP diagrams that allows us to inspect, control and simulate the thermodynamic process of ascending clouds in the atmosphere, as well as a 3D synthetic environment where clouds are advected by buoyant forces. This lightweight physically-based technique enables the incorporation of our cloud simulator in systems tied to important industries, namely movies, virtual environments, and video games.
- CityMii - An integration and interoperable middleware to manage a Smart CityPublication . Cecílio, José; Caldeira, Filipe; Wanzeller, CristinaModern cities are supported by multiple heterogeneous IT systems deployed and managed by distinct agents. In general, those systems use old, dependent and non-standardized technologies, which make them legacy and incompatible systems. As smart cities are moving toward a fully centralized management approach, the lack of integration among systems raises several problems. Since they are independent, it is not easy to correlate information from different systems and put it together to work in order to achieve application goals. The collaboration among different systems enables an agent to offer new functionalities (services or just information about the city) that cannot be provided by any of these systems working as individual entities. The goal of this paper is to propose an integration middleware to support the management of Smart Cities in a dynamic, transparent and scalable way. The proposed middleware intends to support interoperability among different systems operating in a city.
- On the use of ontology data for protecting critical infrastructuresPublication . Henriques, João; Caldeira, Filipe; Cruz, T.; Simões, P.Modern societies increasingly depend on products and services provided by Critical Infrastructures (CI) in areas such as energy, telecommunications and transportation, which are considered vital for their wellbeing. These CIs usually rely on Industrial Automation and Control Systems (IACS), which are becoming larger and more complex due to the increasing amount of available heterogeneous data generated by a raising number of interconnected control and monitoring devices and involved processes. The Security Information and Event Management (SIEM) systems in charge of protecting these CI usually collect and process data from specialized sources, such as intrusion detection systems, log sources, honeypots, network traffic analysers and process control software. However, they usually integrate only a small fraction of the whole data sources existing in the CI. Valuable generic data sources such as human resources databases, staff check clocks, outsourced service providers and accounting data usually fall outside the specialized perimeter of SIEM, despite their potential usefulness for achieving a truly holistic perspective on the CI cybersecurity awareness. One of the main reasons for this state of affairs is the difficulty of integrating such data into the SIEM systems, since it is usually dispersed across multiple databases, using different schema and not originally intended for security-related applications. The process of collecting and adapting data from each of those sources would typically require a long and expensive process of conversion from each database. Moreover, since these databases may change over time (e.g. introduction of new Human Resources information systems), the system is difficult not only to setup but also to properly maintain over time. In order to address this gap, in this paper we propose a framework for making this process easier by using a semantic web approach for automated collection and processing of corporate data from multiple heterogeneous sources. This way, it becomes possible to make these data available, at reasonable costs, in a format which is suitable for security management purposes – especially those related with audit compliance and forensic analysis
- NoSQL Scalability Performance Evaluation over CassandraPublication . Abbasi, Maryam; Sá, Filipe; Albuquerque, Daniel; Wanzeller, Cristina; Caldeira, Filipe; Tomé, P.; Furtado, Pedro; Martins, PedroThe implementation of Smart-Cities is growing all over the world. From big cities to small villages, information able to provide a better and efficient urban management is collected from multiple sources (sensors). Such information has to be stored, queried, analyzed and displayed, aiming to contribute to a better quality of life for citizens and also a more sustainable environment. In this context it is important to choose the right database engine for this scenario. NoSQL databases are now generally accepted by the database community to support application niches. They are known for their scalability, simplicity, and key-indexed data storage, thus, allowing an easy data distribution and balancing over several nodes. In this paper a NoSQL engine is tested, Cassandra, which is one of the most scalable, amongst most NoSQL engines and therefore, a candidate for use in our application scenario. The paper focuses on horizontal scalability, which means that, by adding more nodes, it is possible to respond to more requests with the same or better performance, i.e., more nodes mean reduced execution time. Although, adding more computational resources, does not always result in better performance. This work assesses how each workload (e.g., data volume, simultaneous users) influence scalability performance. An overview of the Cassandra database engine is presented in the paper. Following, it will be tested and evaluated using the benchmark Yahoo Cloud Serving Benchmark (YCSB).
- LowCost system architecture for monitoring environmental parameters in circulating automotive roadsPublication . Costa, João; Wanzeller, Cristina; Albuquerque, Daniel; Caldeira, Filipe; Tomé, P.; Martins, PedroA qualidade de vida nas cidades é cada vez mais uma preocupação. A análise de parâmetros ambientais é nesta base uma preocupação ao nível das entidades responsáveis pela gestão das cidades. Neste artigo apresenta-se uma arquitetura de um sistema de baixo custo para monitorização de parâmetros ambientais em vias de circulação das cidades. Palavras Chave – Cidades Inteligentes, IoT, Arquitetura de Sistema. Abstract — The quality of life in cities is nowadays a concern. The city management authorities usually are concernd with the environmental parameters. This article presents an architecture of a low-cost system for monitoring environmental parameters in Automotive Roads.