Acoustic displacement triangle based on the individual element test

A three node, displacement based, acoustic element is developed. In order to avoid spurious rotational modes, a higher order stiffness is introduced. The higher order stiffness is developed from an incompatible strain field which computes element volume changes under nodal rotational displacements fields. The higher order strain satisfies the IET requirements, non affecting convergence. The higher order stiffness is modulated, element by element, with a factor. Thus, the displacement based formulation is capable of placing the spurious rotational modes over the range of physical compressional modes that can be accurately captured by the mesh

State of the art of pricing policy in air transportation: network carriers vs. low-cost airlines

The modern air transport industry is highly competitive. To survive in the market, the implementation of a successful marketing strategy is fundamental. In particular, an effective pricing policy has become crucial for airlines to remain profitable. Correspondingly, the different types of airline in the market have also established very distinct pricing policies. The present study is based on a literature review and presents the state of the art of pricing policy in air transportation. The aim is to compare and discuss the pricing strategies of network carriers and low-cost airlines. Special attention is paid to Revenue Management, which is a very important management tool used by airlines to take advantage of the differences in willingness to pay of passengers. The pricing policy, however, depends on the overall business strategy of the airline. Results show many differences, resulting from the fact that these two types of airline are characterized by very different fundamental business models and, correspondingly, also target groups. Since network carriers and also low-cost airlines have adjusted their pricing strategies lately, these recent developments will be discussed as well. This paper adds to the knowledge of this topic because it presents the most up-to-date and complete study on pricing regarding network carriers vs. low-cost airlines.A moderna indústria do transporte aéreo é altamente competitiva. Para sobreviver no mercado, a implementação de uma estratégia de marketing bem-sucedida é fundamental. Em particular, uma política de preços eficaz tornou-se crucial para as companhias aéreas continuarem lucrativas. Os diferentes tipos de companhias aéreas no mercado também estabeleceram políticas de preços muito distintas. O presente estudo baseia-se numa revisão da literatura e apresenta o estado da arte da política de preços no transporte aéreo. O objetivo é comparar e discutir as estratégias de preços de companhias aéreas de linha e companhias aéreas de baixo custo. Atenção especial é dada à Gestão de Receitas (Revenue Management), que é uma ferramenta de gestão usada pelas companhias aéreas para aproveitar as diferenças na disposição de pagar dos passageiros. A política de preços, no entanto, depende da estratégia geral de negócios da companhia aérea. Os resultados mostram muitas diferenças, resultantes do facto de que esses dois tipos de companhias aéreas são caracterizados por modelos de negócios fundamentais muito diferentes e, correspondentemente, também grupos-alvo. Como as operadoras de rede e também as companhias aéreas de baixo custo ajustaram as suas estratégias de preços ultimamente, esses desenvolvimentos recentes também serão discutidos. Este documento contribui para o conhecimento deste tópico, pois apresenta o estudo mais atualizado e completo sobre preços de companhias aéreas de linha versus companhias aéreas de baixo custo.info:eu-repo/semantics/publishedVersio

On Nikodym and Rainwater sets for ba (R) and a Problem of M. Valdivia

[EN] If R is a ring of subsets of a set Omega and ba (R) is the Banach space of bounded finitely additive measures defined on R equipped with the supremum norm, a subfamily Delta of R is called a Nikodym set for ba (R) if each set {mu(a) : alpha is an element of A} in ba (R) which is pointwise bounded on Delta is norm-bounded in ba (R). If the whole ring R is a Nikodym set, R is said to have property (N), which means that R satisfies the Nikodym-Grothendieck boundedness theorem. In this paper we find a class of rings with property (N) that fail Grothendieck's property (G) and prove that a ring R has property (G) if and only if the set of the evaluations on the sets of R is a so-called Rainwater set for ba(R). Recalling that R is called a (wN)-ring if each increasing web in R contains a strand consisting of Nikodym sets, we also give a partial solution to a question raised by Valdivia by providing a class of rings without property (G) for which the relation (N) double left right arrow (wN) holds.The first and the third authors are supported by Grant PGC2018-094431-B-I00 of the Ministry of Science, Innovation and Universities of Spain.Ferrando, JC.; López Alfonso, S.; López Pellicer, M. (2019). On Nikodym and Rainwater sets for ba (R) and a Problem of M. Valdivia. Filomat. 33(8):2409-2416. https://doi.org/10.2298/FIL1908409FS2409241633

Covering Properties of Cp(X) and Ck(X)

[EN] Let X be a Tychonoff space. We survey some classic and recent results that characterize the topology or cardinality of X when C-p (X) or C-k (X) is covered by certain families of sets (sequences, resolutions, closure-preserving coverings, compact coverings ordered by a second countable space) which swallow or not some classes of sets (compact sets, functionally bounded sets, pointwise bounded sets) in C(X).Research supported by Grant PGC2018-094431-B-I00 of Ministry of Science, Innovation & Universities of Spain.Ferrando, JC.; López Pellicer, M. (2020). Covering Properties of Cp(X) and Ck(X). Filomat. 34(11):3575-3599. https://doi.org/10.2298/FIL2011575FS35753599341

Psychological elements explaining the consumer's adoption and use of a website recommendation system: A theoretical framework proposal

The purpose of this paper is to understand, with an emphasis on the psychological perspective of the research problem, the consumer's adoption and use of a certain web site recommendation system as well as the main psychological outcomes involved. The approach takes the form of theoretical modelling. Findings: A conceptual model is proposed and discussed. A total of 20 research propositions are theoretically analyzed and justified. Research limitations/implications: The theoretical discussion developed here is not empirically validated. This represents an opportunity for future research. Practical implications: The ideas extracted from the discussion of the conceptual model should be a help for recommendation systems designers and web site managers, so that they may be more aware, when working with such systems, of the psychological process consumers undergo when interacting with them. In this regard, numerous practical reflections and suggestions are presented

Spaces C(X)with ordered bases

[EN] The concept of Sigma-base of neighborhoods of the identity of a topological group G is introduced. If the index set Sigma subset of N-N is unbounded and directed (and if additionally each subset of Sigma which is bounded in N-N has a bound at Sigma) a base {U-alpha : alpha is an element of Sigma} of neighborhoods of the identity of a topological group G with U-beta subset of U-alpha whenever alpha <= beta with alpha, beta is an element of Sigma is called a Sigma-base (a Sigma(2)-base). The case when Sigma = N-N has been noticed for topological vector spaces (under the name of G-base) at [2]. If X is a separable and metrizable space which is not Polish, the space C-c(X) has a Sigma-base but does not admit any G-base. A topological group which is Frechet-Urysohn is metrizable iff it has a Sigma(2)-base of the identity. Under an appropriate ZFC model the space C-c (omega(1)) has a Sigma(2)-base which is not a G-base. We also prove that (i) every compact set in a topological group with a Sigma(2)-base of neighborhoods of the identity is metrizable, (ii) a C-p (X) space has a Sigma(2)-base iff X is countable, and (iii) if a space C-c(X) has a Sigma(2)-base then X is a C-Suslin space, hence C-c(X)is angelic. (C) 2016 Elsevier B.V. All rights reserved.Supported by Grant PROMETEO/2013/058 of the Conselleria de Education, Investigacion, Cultura y Deportes of Generalitat Valenciana. The second author also supported by the GACR Project 16-34860L and RVO: 67985840Ferrando, JC.; Kakol, J.; López Pellicer, M. (2016). Spaces C(X)with ordered bases. Topology and its Applications. 208:30-39. https://doi.org/10.1016/j.topol.2016.05.006S303920

Autonomous UAV System for Cleaning Insulators in Power Line Inspection and Maintenance

The inspection and maintenance tasks of electrical installations are very demanding. Nowadays, insulator cleaning is carried out manually by operators using scaffolds, ropes, or even helicopters. However, these operations involve potential risks for humans and the electrical structure. The use of Unmanned Aerial Vehicles (UAV) to reduce the risk of these tasks is rising. This paper presents an UAV to autonomously clean insulators on power lines. First, an insulator detection and tracking algorithm has been implemented to control the UAV in operation. Second, a cleaning tool has been designed consisting of a pump, a tank, and an arm to direct the flow of cleaning liquid. Third, a vision system has been developed that is capable of detecting soiled areas using a semantic segmentation neuronal network, calculating the trajectory for cleaning in the image plane, and generating arm trajectories to efficiently clean the insulator. Fourth, an autonomous system has been developed to land on a charging pad to charge the batteries and potentially fill the tank with cleaning liquid. Finally, the autonomous system has been validated in a controlled outdoor environment.Ministerio de Ciencia e Innovación (CDTI) AERIAL-CORE H2020 ICT-10-2019-2020FEDER INTERCONECT

Migration Patterns in Male Great Bustards (Otis tarda)

5 paginas, 1 figura y 1 tableThe Great Bustard (Otis tarda) is distributed from Iberia and Morocco in the west to China in the east and has been considered sedentary in all but the northern and eastern parts of its range (Gewalt 1959, Glutz et al. 1973, Cramp and Simmons 1980). However, some studies have reported seasonal changes in population numbers in different areas in the Iberian Peninsula (Hidalgo and Carranza 1990, Alonso et al. 1995), suggesting that the species is a partial migrant (sensu Terrill and Able 1988) in this region. We describe seasonal movements of marked adult male Great Bustards and discuss observed patterns in relation to the following questions: (1) Do migratory males display interannual fidelity to breeding and postbreeding areas? (2) Do males travel significantly farther than females in their seasonal movements? We also suggest several hypotheses that could explain patterns of partial and differential migration in male Great Bustards.This study is a contribution to DGICYT-project PB94–0068.Peer reviewe

Evaluation of captive breeding as a method to conserve threatened Great Bustard populations.

6 paginas y 1 tableThe recent Great Bustard Action Plan summarizes de main recommended lines of action to preserve current populations and their habitats in Europe. Among others, captive breeding is mentioned as a method to save clutches found in the field whose hatching success probability is suspected to be low for any reason. Birds hatched from these clutches have been used to either build up small captive-breeding flocks that ensure preservation of the genetic pool of seriously threatened populations once these may be extinct, or to be released into the natural populations as juveniles. In this paper we evaluate the viability of captive breeding in the light of new results of a recent study of juvenile Great Bustards during their maternal dependence period, family break-up and dispersal. The few data available on survival of captive-bred young after being released suggest that they suffer a high mortality, probably due to the lack of the experience acquired in natural conditions from their mothers. The negative effects of imprinting by their human keepers, particularly in relation with display and mating, has not been sufficiently investigated. These and other aspects make captive breeding questionable as an effective method, as compared with habitat protection measures.PB94-0068 of the Dirección General de Investigacion Cientifica y TecnicaPeer reviewe

Acoustoelastic Pure-Displacement Elements Based on Biot's Poromechanics Theory

From the elastic energy contained in a displacement based porous material the general form of the stiffness and mass matrices are obtained. If both fields can be expanded with equal order polynomials the general form is further simplified and it is shown that the coupling stiffness reduces to the one arising to compute volume changes in an elastic medium. A plane beam and a four node tetrahedron are developed. To avoid spurious rotational modes appearance in the tetrahedron fluid a penalty formulation is used. The effect of the penalty factor in matrix conditioning is analysed. Elements dynamic behaviour is compared