A network-wide exact optimization approach for multiobjective routing with path protection in multiservice multiprotocol label switching networks

A multiobjective routing model for multiprotocol label switching networks with multiple service types and path protection is presented in this article. The routing problem is formulated as a biobjective integer program, where the considered objectives are formulated according to a network-wide optimization approach, i.e. the objective functions of the route optimization problem depend explicitly on all traffic flows in the network. A disjoint path pair is considered for each traffic trunk, which guarantees protection to the associated connection. A link-path formulation is proposed for the problem, in which a set of possible pairs of paths is devised in advance for each traffic trunk. An exact method (based on the classical constraint method for solving multiobjective problems) is developed for solving the formulated problem. An extensive experimental study, with results on network performance measures in various randomly generated networks, is also presented and discussed.     

Substrate influences on the properties of SnS thin films deposited by chemical spray pyrolysis technique for photovoltaic applications

Herein, we report on tin monosulfide (SnS) thin films elaborated by the Chemical Spray Pyrolysis (CSP) technique onto various substrates as simple glass, ITO-, and Mo-coated glasses in order to study the influence of substrates on the physical and chemical properties of Sns thin films. Structural analysis revealed that all films crystallize in orthorhombic structure with (111) as the sole preferential direction without secondary phases. In addition, film prepared onto pure glass exhibits a better crystallization compared to films deposited onto coated glass substrates. Raman spectroscopy analysis confirms the results obtained by X-ray diffraction with modes corresponding well to SnS single-crystal orthorhombic ones (47, 65, 94, 160, 186, and 219 cm ^?1) without any additional parasite secondary phase like Sn₂S₃ or SnS₂. Field emission scanning electron microscope revealed that all films have a cornflake-like particles surface morphology, and energy dispersive X-ray spectroscopy analysis showed the presence of sulfur and tin with a nearly stoichiometric ratio in films deposited onto pure glass. High surface roughness and large grains are observable in film deposited onto glass. From optical spectroscopy, it is inferred that band gap energy of SnS/glass and SnS/ITO were 1.64 and 1.82 eV, respectively.     

Wave finite element‐based superelements for forced response analysis of coupled systems via dynamic substructuring

The wave finite element (WFE) method is used for assessing the harmonic response of coupled mechanical systems that involve one‐dimensional periodic structures and coupling elastic junctions. The periodic structures under concern are composed of complex heterogeneous substructures like those encountered in real engineering applications. A strategy is proposed that uses the concept of numerical wave modes to express the dynamic stiffness matrix (DSM), or the receptance matrix (RM), of each periodic structure. Also, the Craig–Bampton (CB) method is used to model each coupling junction by means of static modes and fixed‐interface modes. An efficient WFE‐based criterion is considered to select the junction modes that are of primary importance. The consideration of several periodic structures and coupling junctions is achieved through classic finite element (FE) assembly procedures, or domain decomposition techniques. Numerical experiments are carried out to highlight the relevance of the WFE‐based DSM and RM approaches in terms of accuracy and computational savings, in comparison with the conventional FE and CB methods. The following test cases are considered: a 2D frame structure under plane stresses and a 3D aircraft fuselage‐like structure involving stiffened cylindrical shells. Copyright © 2015 John Wiley & Sons, Ltd.     

On admissible total orders for typical hesitant fuzzy consensus measures

In this paper, we discussconsensus measures for typical hesitant fuzzy elements (THFE), which are the finite and nonempty fuzzy membership degrees under the scope of typical hesitant fuzzy sets (THFS). In our approach, we present a model that formally constructs consensus measures by means of aggregations functions, fuzzy implication-like functions and fuzzy negations, using admissible orders to compare the THFE, and also providing an analysis of consistency on them. Our theoretical results are applied into a problem of decision making with multicriteria illustrating our methodology to achieve consensus in a group of experts working with THFS.     

Stochastic Optimal Coordination of Small UAVs for Target Tracking using Regression-based Dynamic Programming

We study the problem of optimally coordinating multiple fixed-wing UAVs to perform vision-based target tracking, which entails that the UAVs are tasked with gathering the best joint vision-based measurements of an unpredictable ground target. We utilize an analytic expression for the error covariance associated with the fused measurements of the target’s position, and we employ stochastic fourth-order models for all vehicles, thereby incorporating a high degree of realism into the problem formulation. While dynamic programming can generate an optimal control policy that minimizes the expected value of the fused geolocation error covariance over time, it is accompanied by significant computational challenges due to the curse of dimensionality. In order to circumvent this challenge, we present a novel policy generation technique that combines simulation-based policy iteration with a robust regression scheme. The resulting control policy offers a significant advantage over alternative approaches and shows that the optimal control strategy involves coordinating the UAVs’ distances to the target rather than their viewing angles, which had been a common practice in target tracking.     

Multi-objective approach for robot motion planning in search tasks

This work addresses the problem of single robot coverage and exploration in an environment with the goal of finding a specific object previously known to the robot. As limited time is a constraint of interest we cannot search from an infinite number of points. Thus, we propose a multi-objective approach for such search tasks in which we first search for a good set of positions to place the robot sensors in order to acquire information from the environment and to locate the desired object. Given the interesting properties of the Generalized Voronoi Diagram, we restrict the candidate search points along this roadmap. We redefine the problem of finding these search points as a multi-objective optimization one. NSGA-II is used as the search engine and ELECTRE I is applied as a decision making tool to decide among the trade-off alternatives. We also solve a Chinese Postman Problem to optimize the path followed by the robot in order to visit the computed search points. Simulation results show a comparison between the solution found by our method and solutions defined by other known approaches. Finally, a real robot experiment indicates the applicability of our method in practical scenarios.     

The Orientation of Pre-Romanesque Churches in the Iberian Peninsula

The orientation of Christian churches is a distinctive feature of its architecture, repeating patterns from early Christian times that show a general tendency to orientate their apses in the solar range, with a predilection for orientations near the astronomical equinox. We measured the orientation of a total of 167 churches built prior to A.D. 1086. A comprehensive statistical analysis of the sample indicates a decisive orientation pattern, with a clear tendency to orientate according to the standard tradition, albeit with certain particularities. Three sub-samples are examined to find the tendencies at each different historical time. This exercise indicates that the main group of orientations seem to relate to the Canonical equinox on 25 March, while popular ‘expected’ orientations, such as that of the rising sun on the day of the patron saint of the church, are completely absent. Other groups of orientations are specific to each period, such as that towards sunrise on Saint James’s day, important only after the discovery of the saint’s tomb in the ninth century.     

Evaluating user experience in joint activities between schools and museums in virtual worlds

The use of virtual worlds in the school is an extraordinary tool to engage the children in the process of e-learning. Although one can find many examples that describe the use of such a technology in teaching regular educational contents, very few examples replicate other classical outdoor educational activities such as a visit to a museum, including the remote interaction with the docents of the visited institution. In this work, the results of a study of the user experience of three groups of children within a flexible virtual space that connects schools and museums are described and evaluated. This integrated educational space not only includes the exploration of exhibition areas but also the telepresence talks on the part of museum personnel, simulations, educational work in the form of virtual quests, all within a multi-user virtual environment based on OpenSim and simultaneously accessible from the different institutions involved in the experiment. The results obtained could serve as a starting point for a future implementation of this platform for connecting educational institutions and museums across an entire city.     

A two-stage filter for high density salt and pepper denoising

Image restoration is an important and interesting problem in the field of image processing because it improves the quality of input images, which facilitates postprocessing tasks. The salt-and-pepper noise has a simpler structure than other noises, such as Gaussian and Poisson noises, but is a very common type of noise caused by many electronic devices. In this article, we propose a two-stage filter to remove high-density salt-and-pepper noise on images. The range of application of the proposed denoising method goes from low-density to high-density corrupted images. In the experiments, we assessed the image quality after denoising using the peak signal-to-noise ratio and structural similarity metric. We also compared our method against other similar state-of-the-art denoising methods to prove its effectiveness for salt and pepper noise removal. From the findings, one can conclude that the proposed method can successfully remove super-high-density noise with noise level above 90%.