Advances in Science and Technology Vol. 144

Abstract: The Automatic identification system is a system used globally by ships that allows the easy identification of other surface contacts (also equipped with an automatic identification system equipment). The main objective of the present work is to validate experimentally the prediction of a ship's movement. A Kalman Filter algorithm, a recursive technique widely used in several scientific areas of study including navigation, is designed to estimate and predict the movement. In this work, a non-linear kinematic model is proposed to analyse and predict the movement of an automatic identification system contact, based on the data transmitted by it. The results evidence that the automatic identification system data can be used as input of a Kalman filter to get consistent and reliable information, an advantage to decision makers so they can act with adequate knowledge and in time.

Abstract: The development of the technology in the last decades, and, considering the navigation and positioning systems, the appearance of the micro-electro-mechanical systems allowed solutions of positioning and navigation low-cost. Framing this analysis with the environment in which we find ourselves inserted, it was decided to use a Kalman filter that adapted to the recorded measurements of a sensor used on one of the ships of the Portuguese Navy: an anemometer. The anemometer’s function is to measure the direction and relative wind speed felt by the ship. This equipment directly affects the navigation of the ship, not only on a ship like the NRP Sagres, in terms of sailing, for which the knowledge of wind direction and speed is crucial, but for all ships, or when navigating in restricted waters, due to the sinking of the ship caused by the wind, or for a large number of operations, such as maneuvering of the vessel, flight operations, among others. As previously mentioned, this sensor, like many others, is subject to a series of interferences, causing errors, which are still due to possible operating and reading errors by the operator. The objective of this work is to filter the data obtained from measurements of the anemometer at NRP Sagres, with the purpose of reducing the previously mentioned errors. The results are promising and consistent, allowing us count with the expected reliable information.

Abstract: This paper involves a fundamental study of a numerical method for progressive collapse resistance design of floor-to-floor joints in precast cross-wall structures. It presents a 3D numerical study of a floor-to-floor system with longitudinal and transverse ties. The model is also used to derive the post-bond behavior and the mechanism of forming catenary action concerning the bond behavior in precast cross-wall structures. The obtained results indicated the adequacy and applicability of the code specifications in British Standard, Euro Codes, and DoD 2013. Discrepancies in the tie-force between the numerical results and codified specifications have suggested an inappropriate use of the current TF method, hence, an improved model based on the numerical results has been proposed to address this concern. To the authors’ best knowledge, this is the first numerical study to investigate the behavior of floor-to-floor joints following the removal of wall support in typical precast cross-wall structures when considering bar fracture and pull-out failure mode..

Abstract: This paper presents a new analytical model to predict the mechanical behaviour of an elastic straight thin-walled circular tube (pipe) subjected to bending. A thin-walled pipe cannot be modelled as a simple beam, inasmuch it presents a shell-like behaviour due to the ovalization (in-plane warping) of the cross-section when loaded. The section modification implies a non-linear trend between the applied moment and the axial curvature, i.e. a non-invariance of the section moment of inertia. Two analytical ways are proposed in the reference literature: a rigorous one due to Reissner use a stress-function approach, and an approximated one, first due to Brazier, that follows Ritz approach. The Reissner model is analytically unsolvable and difficult to face numerically due to some integral conditions to fulfill. On the contrary, the Ritz approach is easy to implement, but being Heuristic is limited to circular sections. To overcome the previous mentioned difficulties a new geometrically exact Pipe model in terms of displacements is proposed, which turns out to be a mix between a shell and a beam model. The present approach leads to a system of ODEs accompanied by Boundary Value Problems (not requiring any integral conditions) that can be solved using a direct collocation method. After solving it, we build-up the dimensionless (non-linear) moment-curvature diagram, valid for any straight pipe, i.e. for every diameter, thickness, and whatever linear elastic material. The results are compared with other literature solutions performed using the Ritz’s approach and with Finite Element Analysis.

Abstract: 3D printed patient-specific hand orthoses can improve the efficiency of the treatment and the comfort of the patient, but since each customized orthosis is a virtually unique device, it is difficult to assess their mechanical response in the design phase, both experimentally and numerically. The Finite Element Method (FEM) could be used to predict the deformation of the orthosis under predetermined loads, but patient-specific models including interaction with the hand are still lacking. In the present work we present a computational model in which, starting from the scan data of the hand used to manufacture the orthosis, a FEM model of the hand is generated, including a skeletal structure. Hand bones positions and dimensions can be defined basing on simple anatomical measurements or literature data and the stiffness of the joints can be tuned in relation to patient pathology. The remaining hand volume consists of a soft tissue region, mimicking the non-linear mechanical behaviour of skin and muscles. Results show that both functional and structural indexes can be analyzed, such as contact pressures, stress state or the compliance of the orthosis, providing useful information for the design of custom devices. By using mesh deformation algorithms, the scan data could be used to generate different orthosis designs in target positions defined by the therapist and, taking advantage of a parametric model under development, the skeletal structure could be adapted correspondingly, providing an innovative pathway to investigate the response of the orthosis during the whole rehabilitation.

Abstract: This work describes the synthesis and characterization of PolyDiMethylSiloxane/Titanium Dioxide (PDMS/TiO2) biopolymer nanocomposite films using two different synthesis methods: ex-situ and in-situ. The PDMS polymer were filled with titanium dioxide (TiO2) nanoparticles. The effects of varying ratios of TiO2 filler (3%, 5%, 10%, and 15%) on the film properties were investigated. The films were thin, ductile, and varied in transparency depending on the filler ratio. various techniques scanning electron microscopy and optical microscopy were used to characterize the TiO2 nanoparticles and PDMS/TiO2 nanocomposite films. Results showed that the TiO2 nanoparticles had a perfect crystalline nanostructure. The analyses of the nanocomposite films confirmed the establishment of cross-linking between the matrix and the reinforcement. The bathochromic effect was shown in the filled films due to the presence of TiO2 nanoparticles in the polymer matrix. The addition of TiO2 nanoparticles modified the PDMS matrix properties, such as transparency and antibacterial activity, making it suitable for various applications such as food or biomedical packaging. In-situ synthesis resulted in better roughness and thickness due to medium dispersion of nanoparticles in the polymer lattice, as confirmed by optical microscopy. This comparative study demonstrates that both synthesis approaches can be used for PDMS/TiO2 nanocomposite films and provides insights into the advantages and disadvantages of each method and contributes to the development of new materials with unique properties in various sectors of the market.