Correlation between the pivot node concept and fatigue crack closure

The study of fatigue crack growth has been commonly done by means of bi-dimensional models and assuming a homogeneous behaviour through the thickness. According to the specimen thickness, a state of plane stress or plane strain is presumed. However, recently, it has been shown that thickness effects influence the crack tip behaviour. These works have revealed a series of effects along the thickness with a strong influence on the crack front growth. One of the experimental evidences that can be explained as a direct consequence of these effects is the curvature of the crack. It is observed that when the crack advance, the crack front changes adopting a curved shape, growing faster at the interior than at the exterior. Two mechanisms can explain this effect: the first one is related to the crack closure effect near the surface. The second one, related to the plastic zone size decrement observed in a small region close to the surface, is due to ΔK being smaller near the surface than in the interior. Both mechanisms are difficult to evaluate separately. A series of works were devoted to study these effects. A research line has been focused in the analysis of the stress intensity factor distribution. These works evaluate the finite element model of an Al 2024-T35 compact tension specimen with no plastic wake effect introduced, according to the methodology developed by the authors. The three-dimensional behaviour in the vicinity of the crack front is simulated through numerical analysis with ANSYS code and J-integral method is used to determinate the curves of K evolution along the thickness. The main finding of these studies is that the distribution of K is not homogeneous. The overall values for the whole model accurately agree with the nominal K applied. The K profiles along the thickness are characterized by a series of parameters that allow us to analyze the distribution of K in terms of the expected Knom against variations of geometrical and external factors.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Key aspects in 3D fatigue crack closure numerical modelling

Since long time, fatigue crack closure has been studied by means of finite element models. Initially by bi-dimensional models and recently, due to the higher computational capabilities, the use of three-dimensional models has been extended, providing a wider comprehension of the problem. Starting with the methodology used for 2D cases, a specific methodology for 3D models has been developed. Key parameters affecting the model have been analyzed and recommendations have been established. The numerical accuracy is evaluated in terms of crack closure and opening values. They main issues studied are the material behaviour, the loading cycles and crack growth scheme, the contact simulation, the meshing and the element size at the crack tip and along the thickness, the plastic wake computed and the opening and closure definition considered. This paper summarises the main learning and recommendations from the latest numerical modelling experience of the authors.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Diagnóstico de plasma en Tokamak utilizando ondas de Alfvén

Descargue el texto completo en el repositorio institucional de la Universidade de São Paulo: https://doi.org/10.11606/T.43.2015.tde-14082015-110334El trabajo investiga la excitación de automodos de Alfvén en tokamaks, utilizando una descripción realista de las antenas externas a la columna de plasma en los tokamaks TCABR y JET. El modelo teórico de excitación de ondas de Alfvén en una columna de plasma cilíndrico (modos Alfvén globales - GAWs) y el modelo más complejo de las ondas de Alfvén en plasmas toroidales (automodos toroidales de Alfvén - TAEs) son estudiados. La excitación de los modos TAEs en el JET se estudian utilizando los códigos HELENA (reconstruye el equilibrio magnetohidrodinámico) y CASTOR (calcula los campos perturbados asociados a inestabilidades del modelo magnetohidrodinámico resistivo). Determinamos la calidad del espectro y las funciones asociadas a los TAEs, con diferentes números toroidales, excitados por el sistema de antenas. Se investigó el efecto de las fases de las corrientes de alimentación de los diferentes módulos de antenas sobre la calidad del espectro excitado, utilizando un método original, implementado en este trabajo, para utilizar el CASTOR. Los resultados indican que aunque la excitación de un modo dado puede ser privilegiada por una elección óptima de fases, los modos satélite también pueden excitarse con mayor amplitud, de modo que la pureza del espectro no se mejora sustancialmente.In this work we investigated the excitation of Alfvén eigenmodes in tokamaks using external antennas to the plasma column. The basic theory of Alfvén waves is revised, including non-ideal effects such as resistivity. Then the theoretical model for excitation Alfvén waves in a cylindrical plasma column, developed by Kurt Appert, is shown in detail, as an introduction to the more complex problem of Alfvén waves in toroidal plasmas. The cylindrical model is implemented in a numerical code, which is used to study the excitation of Global Alfvén Waves (GAWs), below to the so-called Continuum of Alfvén, in TCABR and JET tokamaks, using a realistic description of their antenna systems. In the sequel, it is given a brief description of Toroidal Alfvén eigenmodes (TAEs) that are excited in the gaps of the Continuum of Alfvén created by the periodicity condition of the toroidal configuration. The excitement of these modes in JET tokamak is studied using the codes HELENA, for reconstruction of magneto-hydrodynamic equilibrium, and CASTOR, which calculates the perturbed fields in this equilibrium, coupled with instability or modes excited within the magneto-resistive hydrodynamic model. This study was carried out in order to determine, consistently, the spectrum quality and the eigenmodes associated with TAEs, with different numbers toroidal n, excited by the new JET antenna system. In particular, it was investigated in detail the effect of the phases of the supply currents of the different modules (eight) of the antenna system in the quality of the excited spectrum, using an original method, implemented in this work, based on the CASTOR code. The results indicate that, although the excitation of a certain mode may be a privileged by an optimized choice of phases, satellite modes can also be excited with higher amplitude, so that the purity of the spectrum is not substantially improved. This is the main result obtained in this work.Brasil. Ministério da Educação. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes

THE ROLE OF THE EUROPEAN UNION AND OTHER INTERNATIONAL ORGANIZATIONS IN THE PROCESS OF THE REGIONALISATION OF THE PEACEKEEPING OPERATIONS

Due to the increase and complexity of conflicts with internal and international caracter the United Nations had to realize that their capacity to protect peace and international security have been surpassed by the caracteristics and dynamics of the conflicts that the international society has been confronted with. In this context the regional organizations had to assume a number of tasks on their own or in cooperation with the United Nations with the objective to contribute to maintaining international peace and security

El proceso de regionalización de las operaciones de mantenimiento de la paz y su implementación práctica

Ante el incremento y complejidad de los conflictos de carácter interno e internacional que se han presentado en el escenario internacional, las Naciones Unidas, han visto cómo sus capacidades para proteger la paz y seguridad internacionales han sido superadas por las características y dinámicas de los conflictos. En este contexto, las organizaciones regionales han tenido que asumir una serie de tareas de manera autónoma o en cooperación con las Naciones Unidas con la finalidad de contribuir al mantenimiento de la paz y la seguridad internacionales

Contribution to Reduce the Influence of the Free Sliding Edge on Compression-After-Impact Testing of Thin-Walled Undamaged Composites Plates

[EN] Standard Compression-After-Impact test devices show a weakening effect on thin-walled specimens due to a free panel edge that is required for compression. As a result, thin-walled undamaged samples do not break in the free measuring area but near the free edge and along the supports. They also show a strength reduction due to the free edge which can become potentially relevant for very weakly damaged panels. In order to reduce the free edge influence on the measured strength, a modified Compression-After-Impact test device has been developed. In an experimental investigation with carbon fiber reinforced plastics, the modified device is compared with a standard device. It is shown that thin-walled undamaged specimens investigated with the modified device now mainly break within the free measuring area and no longer at the free edge and along the bearings as it is the case for standard test devices. The modified device does not cause a free edge weakening effect in comparison to standard devices. The modified device is therefore more suitable for determining the compression strengths of undamaged thin-walled composite platesThis research was partially supported by the Spanish government under grant number DPI2013-44903-R-AR through funding the specimens as well as the CAI-standard device. The Article Processing Charge is also funded under that grant number.Linke, M.; García Manrique, JA. (2018). Contribution to Reduce the Influence of the Free Sliding Edge on Compression-After-Impact Testing of Thin-Walled Undamaged Composites Plates. Materials. 11(9):1708-1721. doi:10.3390/ma11091708S1708172111

UN MODELO LÓGICO-FORMAL PARA EL ESTUDIO DE LOS ARGUMENTOS EMOCIONALES EN LOS PROCESOS DE CONSTRUCCIÓN DE ACUERDOS/ A LOGICAL-FORMAL MODEL FOR THE STUDY OF EMOTIONAL ARGUMENTS IN NEGOTIATION PROCESSES/ UM MODELO LÓGICO-FORMAL PARA O ESTUDO DOS ARGUMENTOS EMOCIONAIS NOS PROCESSOS DE CONSTRUÇÃO DE ACORDOS

Los argumentos son parte de un proceso comunicativo con el cual se trata de incidir en la acción de otros. Gilbert (1994) identifica cuatro modos de argumentación: el modo lógico, el modo emocional, el modo visceral y el modo kisceral. Siguiendo la línea de investigación en psicología computacional marcada por Ortony, Clore y Collins (1988) y el modelo de resolución de conflictos usando negociaciones basadas en argumentos propuesto por Jung y Tambe (2001), este trabajo presenta un modelo lógico-formal para el estudio de un modo concreto de argumentos emocionales dentro del contexto de formación de consensos enmarcado en un proceso de negociación/coordinación. Se discuten sus implicaciones en los modelos cognitivos emocionales basados en el proceso de apreciación/evaluación de la emoción

The main component of an alarm pheromone of kissing bugs plays multiple roles in the cognitive modulation of the escape response

Innate responses in animals can be modulated by experience. Disturbed adults of the triatomine bug Triatoma infestans release an alarm pheromone (AP) that elicits an escape response in conspecific larvae. The main component of this AP, the isobutyric acid (IsoAc), alone has already shown to generate an escape response in this species. However, not much is known about the modulation of this behavior by non-associative and associative cognitive processes. We present here evidences of the cognitive capacities of T. infestans larvae in an escape context under different conditioning paradigms, including IsoAc in different roles. We show that: (1) the duration of a pre-exposure to IsoAc plays a main role in determining the type of non-associative learning expressed: short time pre-exposures elicit a sensitization while a longer pre-exposure time triggers a switch from repellence to attractiveness; (2) a simple pre-exposure event is enough to modulate the escape response of larvae to the AP and to its main component: IsoAc; (3) IsoAc and the AP are perceived as different chemical entities; (4) an association between IsoAc and an aversive stimulus can be created under a classical conditioning paradigm; (5) an association between IsoAc and a self-action can be generated under an operant conditioning. These results evince that IsoAc can attain multiple and different cognitive roles in the modulation of the escape response of triatomines and show how cognitive processes can modulate a key behavior for surviving, as it is the escaping response in presence of a potential danger in insects.Fil: Minoli, Sebastian Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Palottini, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Manrique, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentin

The Influence of Small-Scale Sporting Events on Participants’ Intentions to Recommend the Host City

Tourism, including sports tourism, is an important driver of social and economic development. Sports tourism events, and small-scale sporting events in particular, are a powerful resource for promoting tourism in the host city, as a viable way of developing sustainable tourism in the local community. This study aims to analyse the impact of functional quality, outcome quality, satisfaction, and perceived value on intentions to recommend the host city among participants in a small-scale sporting event. A total of 866 runners in a 21-km recreational race participated in this study. A multi-item scale was used and a confirmatory factor analysis of the model was carried out, and the presence of gender differences in the relationships was ascertained using a multigroup analysis. The results revealed a direct effect of functional quality and satisfaction, and an indirect effect of outcome quality and value on intentions to recommend the city. Intention to recommend the city and functional quality showed differences between males and females. In conclusion, managing quality is a key strategy in encouraging participants in small-scale sporting events to recommend the host city.Spanish Government PRX 16/0036

Effective photon mass and exact translating quantum relativistic structures

Using a variation of the celebrated Volkov solution, the Klein-Gordon equation for a charged particle is reduced to a set of ordinary differential equations, exactly solvable in specific cases. The new quantum relativistic structures can reveal a localization in the radial direction perpendicular to the wave packet propagation, thanks to a non-vanishing scalar potential. The external electromagnetic field, the particle current density and the charge density are determined. The stability analysis of the solutions is performed by means of numerical simulations. The results are useful for the description of a charged quantum test particle in the relativistic regime, provided spin effects are not decisive