Nearly inviscid Faraday waves in containers with broken symmetry

In the weakly inviscid regime parametrically driven surface gravity-capillary waves generate oscillatory viscous boundary layers along the container walls and the free surface. Through nonlinear rectification these generate Reynolds stresses which drive a streaming flow in the nominally inviscid bulk; this flow in turn advects the waves responsible for the boundary layers. The resulting system is described by amplitude equations coupled to a Navier-Stokes-like equation for the bulk streaming flow, with boundary conditions obtained by matching to the boundary layers, and represents a novel type of pattern-forming system. The coupling to the streaming flow is responsible for various types of drift instabilities of standing waves, and in appropriate regimes can lead to the presence of relaxations oscillations. These are present because in the nearly inviscid regime the streaming flow decays much more slowly than the waves. Two model systems, obtained by projection of the Navier-Stokes-like equation onto the slowest mode of the domain, are examined to clarify the origin of this behavior. In the first the domain is an elliptically distorted cylinder while in the second it is an almost square rectangle. In both cases the forced symmetry breaking results in a nonlinear competition between two nearly degenerate oscillatory modes. This interaction destabilizes standing waves at small amplitudes and amplifies the role played by the streaming flow. In both systems the coupling to the streaming flow triggered by these instabilities leads to slow drifts along slow manifolds of fixed points or periodic orbits of the fast system, and generates behavior that resembles bursting in excitable systems. The results are compared to experiments

Comentarios al dossier“¿Cómo se piensa lo ‘queer’ en América Latina”?

A partir del dossier de Íconos, 39, ¿Cómo se piensa lo ‘queer’ en América Latina?, este artículo trabajasobre los puntos centrales y las interrogantes que dan de sí cada uno de los artículos que locomponen. Destaca la crítica a la masculinidad hegemónica desde una noción de la alteridad enla que convergen las categorías de clase, etnia, género y edad. A medida que reflexiona sobre estospuntos, repasa cada uno de los artículos contextualizándolos en la crítica radical al sistema heteronormativo

Dynamics of counterpropagating waves in parametrically forced, large aspect ratio, nearly conservative systems with nonzero detuning

The dynamics of parametrically driven, slowly varying counterpropagating wave trains in nearly conservative systems are considered. The system is assumed to be invariant under reflection and translations in one direction, and periodic boundary conditions with period L are imposed, with L large but not too large in order that the effect of detuning be significant. The dynamics near the minima of the resulting resonance tongues are described by a system of coupled nonlocal Schrödinger equations with damping and parametric forcing. Elsewhere the long time behavior of the system is described by a damped complex Duffing equation with real coefficients, whose solutions relax to spatially uniform standing waves. Near the bicritical points where two adjacent resonance tongues intersect a pair of coupled damped complex Duffing equations captures the properties of both pure and mixed modes, and of the periodic solutions resulting from a Hopf bifurcation on the branch of mixed modes. As an application, we consider a Faraday system in an annulus in which a pair of counterpropagating surface gravity-capillary waves are excited parametrically by vertical vibration of the container, including the mean flow driven by time-averaged Reynolds stresses due to oscillatory viscous boundary layers along the bottom and the free surface. This mean flow is shown to have a large effect near the bicritical point, where the mean flow changes the dynamics of the system both quantitatively and qualitatively. In particular, inclusion of the mean flow permits Hopf bifurcations from the branches of pure standing waves, and parity-breaking bifurcations from mixed modes

Mejoras de procesos aplicando herramientas de calidad en la recepción de mercadería para reducir los costos e incrementar el nivel de servicio de la empresa Yobel SCM Logistics

RESUMEN El presente trabajo se elaboró con el objetivo de realizar un diseño de plan de mejoramiento en el proceso de recepción de mercadería para reducir los costos actuales operacionales de la empresa Yobel SCM Logístics que ofrece servicios tercerizados de manejo de cadenas de suministros. Este estudio se desarrolló con el fin de conocer, evaluar, documentar, diseñar y proponer mejora continua en el área de recepción. Para llevar a cabo esta propuesta, como punto inicial se realiza el diagnóstico de la situación actual del área de recepción, con el objetivo de identificar y corregir falencias y operaciones innecesarias que impiden obtener una mayor productividad. Además, se identificó que actualmente no se hacía el seguimiento de las actividades lo que originaba incumplimientos en los ingresos de mercadería al sistema por falta de planificación y supervisión. Para el desarrollo de la propuesta, debido a la mala gestión en el proceso de recepción de mercadería, se planteó mejorar a través de herramientas de Calidad, procedimientos, 5s y capacitaciones. PALABRAS CLAVE: gestión logística, gestión de cadena de suministro, cadena de suministro, servicio al cliente, sistema logístico, flujo de bienes y servicios.ABSTRACT This work was developed with the objective of designing an improvement plan in the process of receiving merchandise to reduce the current operating costs of the Yobel SCM logistics company that offers outsourced supply chain management services. This study was developed in order to know, evaluate, document, design and propose a policy of continuous improvement in the reception area. As a starting point the diagnosis of the current situation of the reception area is made, with the aim of identifying and correcting flaws and unnecessary operations that prevent obtaining a higher productivity. In addition, it was identified that activities were not currently being followed, which caused defaults in merchandise revenues to the system due to lack of planning and supervision. For the development of the proposal, due to poor management in the process of receiving merchandise, it was proposed to improve through Quality tools, procedures, 5s and training. KEYWORDS logistics management, supply chain management, supply chain, customer service, logistic system, flow of goods and services

Plant Lectins with Insecticidal and Insectistatic Activities

Lectins are an important group of proteins which are spread in all kingdoms of life. Their most lighted characteristic is associated to their specific carbohydrate binding, although function has been not even identified. According to their carbohydrate specificity, several biological activities have been assessed, finding that lectins can be used as mitogenic agents, biomarkers, and cytotoxic and insecticide proteins. Lectins have been classified according to several features such as structure, source, and carbohydrate recognition. The Protein Research Group (PRG) has worked on Colombian seeds from the family of Fabaceae and Lamiaceae plants, isolating and characterizing their lectins, and found more than one lectin in some plants, indicating that according to its specificity, different lectins can have different biological activities. In the case of legume domain lectins, they have shown the biggest potential as insecticide or insectistatic agents due to the glycosylation pattern in insect midgut cells. This review attempts to identify the characteristics of plant legume lectin domains that determine their insecticidal and insectistatic activities

Dynamics of counterpropagating waves in parametrically forced systems

Parametrically driven waves in weakly dissipative systems with one extended dimension are considered. Multiple scale techniques are used to derive amplitude equations describing the interaction between counterpropagating waves. Dissipation, detuning and forcing are all assumed to be weak and any coupling to mean fields (such as large scale flows in fluid systems) is ignored. If the aspect ratio is moderately large the system is described by a pair of nonlocal equations for the (complex) amplitudes of the waves. The dynamics of these equations are studied both in annular and bounded geometries with lateral walls. The equations admit spatially uniform solutions in the form of standing waves and spatially nonuniform solutions with both simple and complex time-dependence. Transitions among these states are investigated as a function of the driving in three particular cases

Relaxation oscillations in a nearly inviscid Faraday system

In the nearly inviscid regime parametrically driven surface gravity-capillary waves couple to a streaming flow driven in oscillatory viscous boundary layers. In an elliptical container of small eccentricity this coupling can lead to relaxation oscillations

Long-wave Marangoni instability with vibration

The effect of vertical vibration on the long-wave instability of a Marangoni system is studied. The vibration augments the stabilizing effect of surface tension in bounded systems. In laterally unbounded systems nonlinear terms can stabilize non-flat states and prevent the appearance of dry spots. The effect of a slight inclination of the system is also considered

Coupled Amplitude-Streaming Flow Equations for Nearly Inviscid Faraday Waves in Small Aspect Ratio Containers

We derive a set of asymptotically exact coupled amplitude-streaming flow ({CASF}) equations governing the evolution of weakly nonlinear nearly inviscid multimode Faraday waves and the associated streaming flow in finite geometries. The streaming flow is found to play a particularly important role near mode interactions. Such interactions come about either through a suitable choice of parameters or through breaking of degeneracy among modes related by symmetry. An example of the first case is provided by the interaction of two nonaxisymmetric modes in a circular container with different azimuthal wavenumbers. The second case arises when the shape of the container is changed from square to slightly rectangular, or from circular to slightly noncircular but with a plane of symmetry. The generation of streaming flow in each of these cases is discussed in detail and the properties of the resulting CASF equations are described. A preliminary analysis suggests that these equations can resolve discrepancies between existing theory and experimental results in the first two of the above cases