Reinforced concrete is one of the most predominant materials in infrastructures throughout the world, hence management of the structures maintenance is an important subject of study in order to slow down the degradati...
Reinforced concrete is one of the most predominant materials in infrastructures throughout the world, hence management of the structures maintenance is an important subject of study in order to slow down the degradation process and to extend a structure lifespan. This work focus on a numerical model to find the best inspection planning for concrete structures under carbonation- induced corrosion, decomposed in three steps: (a) estimate the probability density function for critical failure time, (b) determine the optimal times for inspections sequences maximising its detectability; (c) multi-objective optimisation via frontier analysis to have a final relative ranking of inspection sequences. In short, this work answer the questions: when the inspections should be done and what are the best inspections for a given efficiency metric, under a set of parameters characterising the degradation process and inspection capabilities. Our formulation extend the models in the literature (e.g. detectability function) and its seems that the multidirectional efficiency analysis algorithm used here is better suited for real situations.
In this paper we investigate a novel model of concatenation of a pair of two-dimensional (2D) convolutional codes. We consider finite-support 2D convolutional codes and choose the so-called Fornasini-Marchesini input-...
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This study deals with forecasting economic time series that have strong trends and seasonal patterns. How to best model and forecast these patterns has been a long-standing issue of time series analysis. In this work,...
This study deals with forecasting economic time series that have strong trends and seasonal patterns. How to best model and forecast these patterns has been a long-standing issue of time series analysis. In this work, we propose a Holt-Winters Exponential Smoothing approach to time series forecasting in order to increase the chance of capturing different patterns in the data and thus improve forecasting performance. Therefore, the main propose of this study is to compare the accuracy of Holt-Winters models (additive and multiplicative) for forecasting and to bring new insights about the methods used via this approach. These methods are chosen because of their ability to model trend and seasonal fluctuations present in economic data. The models are fitted to time series of e-commerce retail sales in Portugal. Finally, a comparison is made and discussed.
In this paper we use some classical ideas from linear systems theory to analyse convolutional codes. In particular, we exploit input-state-output representations of periodic linear systems to study periodically time-v...
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We consider an augmented Einstein-Maxwell-scalar model including an axionic-type coupling between the scalar and electromagnetic field. We study dyonic black hole solutions in this model. For the canonical axionic cou...
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We consider an augmented Einstein-Maxwell-scalar model including an axionic-type coupling between the scalar and electromagnetic field. We study dyonic black hole solutions in this model. For the canonical axionic coupling emerging from high energy physics, all charged black holes have axion hair. We present their domain of existence and investigate some physical properties. For other axionic-type couplings, two classes of black hole solutions may coexist in the model: scalar-free Reissner-Nordström black holes and scalarized black holes. We show that in some region of the parameter space the scalar-free solutions are unstable. Then, there is nonuniqueness since new scalarized black hole solutions with the same global charges, which are entropically preferred over the scalar-free solutions and, moreover, emerge dynamically from the instability of the former, also exist.
For the treatment of moderate and severe cases of deformational plagiocephaly, an asymmetrical deformation of the skull, a cranial remodeling orthosis (CRO) is used. For the development of a new CRO concept, a pressur...
For the treatment of moderate and severe cases of deformational plagiocephaly, an asymmetrical deformation of the skull, a cranial remodeling orthosis (CRO) is used. For the development of a new CRO concept, a pressure sensor grid is placed inside the orthosis that will allow the monitoring of excessive pressures and incorrect CRO positioning throughout the treatment. To implement the sensor grid in the CRO, high mobility of the sensor arms structure that joins the several sensors of this grid is required, however, it is intended that this procedure does not damage the printed copper tracks on the sensor structure. In this study, computer simulations were performed to optimize the sensor arm structure geometry, minimizing undesirable mechanical behavior in the sensor structure when subjected to tensile forces and displacements applied during its placement in the CRO. It was observed that the different sensor arm structures geometries have different effects on the mechanical behavior of the sensor structure when subjected to tensile forces and tensile displacement. The zigzag curve geometry presents the best performance based on high mobility without intense strain on the structure that could damage the printed copper tracks.
An important class of codes widely used in applications is the class of convolutional codes. Most of the literature of convolutional codes is devoted to convolutional codes over finite fields. The extension of the con...
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A discrete version of the symmetric duality of Caputo–Torres, to relate left and right Riemann–Liouville and Caputo fractional differences, is considered. As a corollary, we provide an evidence to the fact that in c...
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It has been recently observed that a scalar field with Robin boundary conditions (RBCs) can trigger both a superradiant and a bulk instability for a Bañados-Teitelboim-Zanelli (BTZ) black hole (BH) [1]. To unders...
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It has been recently observed that a scalar field with Robin boundary conditions (RBCs) can trigger both a superradiant and a bulk instability for a Bañados-Teitelboim-Zanelli (BTZ) black hole (BH) [1]. To understand the generality and scrutinize the origin of this behavior, we consider here the superradiant instability of a Kerr BH confined either in a mirrorlike cavity or in anti-de Sitter (AdS) space, triggered also by a scalar field with RBCs. These boundary conditions are the most general ones that ensure the cavity/AdS space is an isolated system and include, as a particular case, the commonly considered Dirichlet boundary conditions (DBCs). Whereas the superradiant modes for some RBCs differ only mildly from the ones with DBCs, in both cases, we find that as we vary the RBCs the imaginary part of the frequency may attain arbitrarily large positive values. We interpret this growth as being sourced by a bulk instability of both confined geometries when certain RBCs are imposed to either the mirrorlike cavity or the AdS boundary, rather than by energy extraction from the BH, in analogy with the BTZ behavior.
We present a generalization of several results of the classical continuous Clifford function theory to the context of fractional Clifford analysis. The aim of this paper is to show how the fractional integro-different...
We present a generalization of several results of the classical continuous Clifford function theory to the context of fractional Clifford analysis. The aim of this paper is to show how the fractional integro-differential hypercomplex operator calculus can be applied to a concrete fractional Stokes problem in arbitrary dimensions which has been attracting recent interest (cf. [1, 6]).
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