720 research outputs found

    Localized Faraday patterns under heterogeneous parametric excitation

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    Faraday waves are a classic example of a system in which an extended pattern emerges under spatially uniform forcing. Motivated by systems in which uniform excitation is not plausible, we study both experimentally and theoretically the effect of heterogeneous forcing on Faraday waves. Our experiments show that vibrations restricted to finite regions lead to the formation of localized subharmonic wave patterns and change the onset of the instability. The prototype model used for the theoretical calculations is the parametrically driven and damped nonlinear Schr\"odinger equation, which is known to describe well Faraday-instability regimes. For an energy injection with a Gaussian spatial profile, we show that the evolution of the envelope of the wave pattern can be reduced to a Weber-equation eigenvalue problem. Our theoretical results provide very good predictions of our experimental observations provided that the decay length scale of the Gaussian profile is much larger than the pattern wavelength.Comment: 10 pages, 9 figures, Accepte

    Using Natural Raw Materials and CEM Approach for the Design of Andean Volcanic Self-Compacting Concretes

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    La actividad volcánica es característica de las zonas sísmicas. En consecuencia, el material volcánico forma parte del paisaje en lugares donde los terremotos son fenómenos naturales comunes. Dado que los residuos volcánicos (VW) muestran actividad puzolánica, la sustitución del cemento Portland (PC) manufacturado por VW es claramente una opción deseable no solo desde el punto de vista económico sino también para reducir las emisiones de CO 2huella dactilar. Por lo tanto, diseñar hormigones con cementos Portland volcánicos (VPC) contribuye claramente a una producción de cemento más limpia. Las actividades de construcción y edificación en zonas sísmicas necesitan utilizar un tipo específico de hormigón: hormigón autocompactante (SCC). El desafío en el que nos enfocamos fue el diseño de SCC usando VPC. El comportamiento de flujo de SCC se caracteriza por un límite elástico bajo, una viscosidad plástica alta y un comportamiento de espesamiento por cizallamiento a cizallamiento alto. Sin embargo, obtener estas sorprendentes propiedades del hormigón no es fácil con los ensayos de flujo de hormigón tradicionales (cono de Abrams, etc.). Además, estos métodos son muy costosos en términos de tiempo y material. Una alternativa que nos permite utilizar la reometría absoluta y que ha sido poco explorada consiste en la sustitución del hormigón por un mortero equivalente. En este estudio se utilizó el denominado mortero equivalente de hormigón (CEM) para obtener formulaciones de HAC con VPC. Las pruebas de minicono confirmaron la ausencia de mezcla en algunas formulaciones de CEM seleccionadas según el cumplimiento de los criterios para SCC. De las respectivas formulaciones del CEM se infirieron tres propuestas concretas. Se adaptaron al estándar europeo SCC según el ensayo de apertura de conos de Abrams.Partial funding for open access charge: Universidad de Málag

    Performance outcome measures in padel: a scoping review

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    Padel is a modern doubles racket sport which has become popular around the world in the last decades. There has been an increase in the quantity of scientific research about this sport in the last years. Therefore, the main objective of this scoping review is to provide an updated contextualization of research regarding padel. PRISMA ScR was used in order to search for articles fulfilling the inclusion criteria in five fields of interest: the anthropometric profile, physiology and physical performance, biomechanics, the epidemiology of injuries, and match analyses Seventy-seven records were included in the study. Padel is an emerging sport both in sport and research terms. This scoping review provides coaches and researchers with all the knowledge available in the five fields of interest. Furthermore, this study enables them to make a map of the current state of the research about padel, and it opens up doors to future investigations. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

    A simulational and theoretical study of the spherical electrical double layer for a size-asymmetric electrolyte: the case of big coions

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    Monte Carlo simulations of a spherical macroion, surrounded by a size-asymmetric electrolyte in the primitive model, were performed. We considered 1:1 and 2:2 salts with a size ratio of 2 (i.e., with coions twice the size of counterions), for several surface charge densities of the macrosphere. The radial distribution functions, electrostatic potential at the Helmholtz surfaces, and integrated charge are reported. We compare these simulational data with original results obtained from the Ornstein-Zernike integral equation, supplemented by the hypernetted chain/hypernetted chain (HNC/HNC) and hypernetted chain/mean spherical approximation (HNC/MSA) closures, and with the corresponding calculations using the modified Gouy-Chapman and unequal-radius modified Gouy-Chapman theories. The HNC/HNC and HNC/MSA integral equations formalisms show good concordance with Monte Carlo "experiments", whereas the notable limitations of point-ion approaches are evidenced. Most importantly, the simulations confirm our previous theoretical predictions of the non-dominance of the counterions in the size-asymmetric spherical electrical double layer [J. Chem. Phys. 123, 034703 (2005)], the appearance of anomalous curvatures at the outer Helmholtz plane and the enhancement of charge reversal and screening at high colloidal surface charge densities due to the ionic size asymmetry.Comment: 11 pages, 7 figure

    Human error assessment in supply chain: case study in road transport services

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    This research presents an approach from cognitive ergonomics in human error for logistics sector, particularly in the case of land freight transport. For this, the Systematic Human Error Reduction and Prediction Approach – SHERPA, and Success Likelihood Index Method - SLIM methods were applied in three companies participating. Errors were identified in the generation of the cost of the service (T1), in the entry of service data (T2), in notifying customers of the news of the service (T3) and, preparation of the documentation for the drivers (T4). Errors whose probability of occurrence ranged from 24.8% to 34.2% were quantified. The reliability of each error was determined as an independent system in which case the result for tasks T1, T2 and T3 was 80% and 75% for T4.Esta investigación presenta un acercamiento desde la ergonomía cognitiva en la determinación del error humano en el sector logístico, particularmente para el caso del transporte terrestre de carga. Para ello se aplicaron los métodos de Systematic Human Error Reduction and Prediction Approach – SHERPA y Success Likelihood Index Method – SLIM en tres empresas participantes del estudio. Se identificaron errores en la generación del costo del servicio (T1), en el ingreso de datos del servicio (T2), en la notificación a los clientes de las novedades del servicio (T3) y en la preparación de la documentación para los conductores (T4). Se cuantificaron los errores cuya probabilidad de ocurrencia oscilaron entre un 24,8% y 34,2%. Se determinó la fiabilidad de cada error como un sistema independiente, en cuyo caso el resultado arrojado para las tareas T1, T2 y T3 fue del 80% y del 75% para T4

    Identifying and preventing burnout in young oncologists, an overwhelming challenge in the COVID-19 era: a study of the Spanish Society of Medical Oncology (SEOM)

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    COVID-19; Esgotament professional; Oncòlegs jovesCOVID-19; Agotamiento profesional; Oncólogos jóvenesCOVID-19; Professional burnout; Young oncologistsBackground Young oncologists are at particular risk of professional burnout, and this could have a significant impact on their health and care of their patients. The coronavirus disease 2019 (COVID-19) pandemic has forced rapid changes in professionals' jobs and training, with the consequent physical and psychological effects. We aimed to characterize burnout levels and determinants in young oncologists, and the effects of the pandemic on their training and health. Methods Two online surveys were conducted among oncology residents and young oncology specialists in Spain. The first addressed professional burnout and its determinants before the COVID-19 pandemic, while the second analyzed the impact of the pandemic on health care organization, training, and physical and psychological health in the same population. Results In total, 243 respondents completed the first survey, and 263 the second; 25.1% reported significant levels of professional burnout. Burnout was more common among medical oncology residents (28.2%), mainly in their second year of training. It was significantly associated with a poor work–life balance, inadequate vacation time, and the burnout score. Nearly three-quarters of respondents (72%) were reassigned to COVID-19 care and 84.3% of residents missed part of their training rotations. Overall, 17.2% of this population reported that they had contracted COVID-19, 37.3% had scores indicating anxiety, and 30.4% moderate to severe depression. Almost a quarter of young oncologists (23.3%) had doubts about their medical vocation. Conclusions Burnout affects a considerable number of young oncologists. The COVID-19 pandemic has had a profound impact on causes of burnout, making it even more necessary to periodically monitor it to define appropriate detection and prevention strategies.This project received funding from the Spanish Society of Medical Oncology (SEOM)

    Coastal subsidence increases vulnerability to sea level rise over twenty first century in Cartagena, Caribbean Colombia

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    Cartagena is subsiding at a higher rate compared to that of global climate-driven sea level rise. We investigate the relative sea level rise (RSLR) and the influence of vertical land movements in Cartagena through the integration of different datasets, including tide gauge records, GPS geodetic subsidence data, and Interferometric Synthetic Aperture Radar (InSAR) observations of vertical motions. Results reveal a long-term rate (\u3e 60 years) of RSLR of 5.98 ± 0.01 mm/yr. The last two decades exhibited an even greater rate of RSLR of 7.02 ± 0.06 mm/yr. GPS subsidence rates range between − 5.71 ± 2.18 and − 2.85 ± 0.84 mm/yr. InSAR data for the 2014–2020 period show cumulative subsidence rates of up to 72.3 mm. We find that geologically induced vertical motions represent 41% of the observed changes in RSLR and that subsidence poses a major threat to Cartagena’s preservation. The geodetic subsidence rates found would imply a further additional RSLR of 83 mm by 2050 and 225 mm by 2100. The Colombian government should plan for the future and serve as an example to similar cities across the Caribbean
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