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- 2-echelon lastmile delivery with lockers and occasional couriersPublication . Santos, André Gustavo dos; Viana, Ana; Pedroso, João PedroWe propose a new approach for the lastmile delivery problem where, besides serving as collecting points of orders for customers, parcel lockers are also used as transshipment nodes in a 2-echelon delivery system. Moreover, we consider that a customer (occasional courier) visiting a locker may accept a compensation to make a delivery to another customer on their regular traveling path. The proposed shared use of the locker facilities – by customers that prefer to self-pick up their orders, and also as a transfer deposit for customers that prefer home delivery – will contribute to better usage of an already available storage capacity. Furthermore, the use of occasional couriers (OCs) brings an extra layer of flexibility to the delivery process and may positively contribute to achieving some environmental goals: although non-consolidation of deliveries may, at first sight, seem negative, by only considering OCs that would go to the locker independently of making or not a delivery on their way home, and their selection being constrained by a maximum detour, the carbon footprint can be potentially reduced when compared to that of dedicated vehicles. We present a mixed-integer linear programming formulation for the problem that integrates three delivery options – depot to locker, depot to locker followed by final delivery by a professional fleet, and depot to locker followed by final delivery by an OC. Furthermore, to assess the impact of OCs’ no show on the delivery process, we extend the formulation to re-schedule the delivery of previous undelivered parcels, and analyze the impact of different no-show rates. Thorough computational experiments show that the use of OCs has a positive impact both on the delivery cost and on the total distance traveled by the dedicated fleets. Experiments also show that the negative impact of no-shows may be reduced by using lockers with higher capacities.
- 2022 - O contexto atual das ITED/ITURPublication . Duarte, Jorge Manuel FerreiraNo ano de 2005, começou a obrigatoriedade de qualquer edifício ter uma infraestrutura ITED (Infraestrutura de Telecomunicações em Edifícios), quer seja na sua construção ou reconstrução. O ponto principal na elaboração do manual na sua primeira edição era de juntar a rede de pares de cobre com a rede de cabo coaxial e de fibra ótica. Por outro, dotar a nível de infraestruturas, mais concretamente a rede tubagens, para a entrada de vários operadores aos clientes, de forma que as infraestruturas não fossem o problema. Notar que, um dos objetivos principais, era que houvesse livre concorrência entre operadores e não houvesse barreiras físicas no fornecimento de serviços aos seus clientes.
- Absolutely stable difference scheme for a general class of singular perturbation problemsPublication . El-Zahar, Essam R.; Alotaibi, A. M.; Ebaid, Abdelhalim; Baleanu, Dumitru; Machado, J. A. Tenreiro; Hamed, Y. S.This paper presents an absolutely stable noniterative difference scheme for solving a general class of singular perturbation problems having left, right, internal, or twin boundary layers. The original two-point second-order singular perturbation problem is approximated by a first-order delay differential equation with a variable deviating argument. This delay differential equation is transformed into a three-term difference equation that can be solved using the Thomas algorithm. The uniqueness and stability analysis are discussed, showing that the method is absolutely stable. An optimal estimate for the deviating argument is obtained to take advantage of the second-order accuracy of the central finite difference method in addition to the absolute stability property. Several problems having left, right, interior, or twin boundary layers are considered to validate and illustrate the method. The numerical results confirm that the deviating argument can stabilize the unstable discretized differential equation and that the new approach is effective in solving the considered class of singular perturbation problems.
- Accessing complexity from genome informationPublication . Machado, J. A. TenreiroThis paper studies the information content of the chromosomes of 24 species. In a first phase, a scheme inspired in dynamical system state space representation is developed. For each chromosome the state space dynamical evolution is shed into a two dimensional chart. The plots are then analyzed and characterized in the perspective of fractal dimension. This information is integrated in two measures of the species’ complexity addressing its average and variability. The results are in close accordance with phylogenetics pointing quantitative aspects of the species’ genomic complexity.
- Active Replication: Towards a Truly SRAM-based FPGA On-Line Concurrent TestingPublication . Gericota, Manuel G.; Alves, Gustavo R.; Silva, Miguel L.; Ferreira, J. M. MartinsThe reusing of the same hardware resources to implement speed-critical algorithms, without interrupting system operation, is one of the main reasons for the increasing use of reconfigurable computing platforms, employing complex SRAM-based FPGAs. However, new semiconductor manufacturing technologies increase the probability of lifetime operation failures, requiring new on-line testing / fault-tolerance methods able to improve the dependability of the systems where they are included. The Active Replication technique presented in this paper consists of a set of procedures that enables the implementation of a truly non-intrusive structural on-line concurrent testing approach, detecting and avoiding permanent faults and correcting errors due to transient faults. In relation to a previous technique proposed by the authors as part of the DRAFT FPGA concurrent test methodology, the Active Replication technique extends the range of circuits that can be replicated, by introducing a novel method with very low silicon overhead.
- Adomian Decomposition and Fractional Power Series Solution of a Class of Nonlinear Fractional Differential EquationsPublication . Mohammed, Pshtiwan Othman; Machado, J. A. Tenreiro; Guirao, Juan L. G.; Agarwal, Ravi P.Nonlinear fractional differential equations reflect the true nature of physical and biological models with non-locality and memory effects. This paper considers nonlinear fractional differential equations with unknown analytical solutions. The Adomian decomposition and the fractional power series methods are adopted to approximate the solutions. The two approaches are illustrated and compared by means of four numerical examples.
- Advances in fractional differential equations (IV): Time-fractional PDEsPublication . Zhou, Yong; Feckan, Michal; Liu, Fawang; Machado, J. A. TenreiroThe fractional calculus (FC) started more than three centuries ago. In the last years, FC is playing a very important role in various scientific fields. In fact, FC has been recognized as one of the best tools to describe long-memory processes. Fractional-order models are interesting not only for engineers and physicists, but also for mathematicians. Among such models those described by partial differential equations (PDEs) containing fractional derivatives are of utmost importance. Their evolution was more complex than for the classical integer-order counterpart. Nonetheless, classical PDEs’ methods are hardly applicable directly to fractional PDEs. Therefore, new theories and methods are required, with concepts and algorithms specifically developed for fractional PDEs. This is the fourth special issue on Advances in Fractional Differential Equations of the journal Computers and Mathematics with Applications. This selection of 38 papers focuses on innovative theoretical and numerical methods, and in applications of FC to important problems that encompass the most relevant areas of current research on fractional PDEs.
- An efficient local meshless approach for solving nonlinear time-fractional fourth-order diffusion modelPublication . Nikan, O.; Avazzadeh, Z.; Machado, J. A. TenreiroThis paper adopts an efficient meshless approach for approximating the nonlinear fractional fourth-order diffusion model described in the Riemann–Liouville sense. A second-order difference technique is applied to discretize temporal derivatives, while the radial basis function meshless generated the finite difference scheme approximates the spatial derivatives. One key advantage of the local collocation method is the approximation of the derivatives via the finite difference formulation, for each local-support domain, by deriving the basis functions expansion. Another advantage of this method is that it can be applied in problems with non-regular geometrical domains. For the proposed time discretization, the unconditional stability is examined and an error bound is obtained. Numerical results illustrate the applicability and validity of the scheme and confirm the theoretical formulation.
- An efficient numerical scheme for solving multi-dimensional fractional optimal control problems with a quadratic performance indexPublication . Bhrawy, A. H.; Doha, E.H.; Machado, J. A. Tenreiro; Ezz-Eldien, S. S.The shifted Legendre orthogonal polynomials are used for the numerical solution of a new formulation for the multi-dimensional fractional optimal control problem (M-DFOCP) with a quadratic performance index. The fractional derivatives are described in the Caputo sense. The Lagrange multiplier method for the constrained extremum and the operational matrix of fractional integrals are used together with the help of the properties of the shifted Legendre orthonormal polynomials. The method reduces the M-DFOCP to a simpler problem that consists of solving a system of algebraic equations. For confirming the efficiency and accuracy of the proposed scheme, some test problems are implemented with their approximate solutions.
- An Efficient Operational Matrix Technique for Multidimensional Variable-Order Time Fractional Diffusion EquationsPublication . Zaky, M. A.; Ezz-Eldien, S. S.; Doha, E. H.; Machado, J. A. Tenreiro; Bhrawy, A. H.This paper derives a new operational matrix of the variable-order (VO) time fractional partial derivative involved in anomalous diffusion for shifted Chebyshev polynomials. We then develop an accurate numerical algorithm to solve the 1þ1 and 2þ1 VO and constant-order fractional diffusion equation with Dirichlet conditions. The contraction of the present method is based on shifted Chebyshev collocation procedure in combination with the derived shifted Chebyshev operational matrix. The main advantage of the proposed method is to investigate a global approximation for spatial and temporal discretizations, and it reduces such problems to those of solving a system of algebraic equations, which greatly simplifies the solution process. In addition, we analyze the convergence of the present method graphically. Finally, comparisons between the algorithm derived in this paper and the existing algorithms are given, which show that our numerical schemes exhibit better performances than the existing ones.