Reply to comment by B. Andreotti et al. on "Solving the mystery of booming sand dunes"

This reply addresses three main issues raised in the comment of Andreotti et al. [2008]. First, the turning of ray paths in a granular material does not preclude the propagation of body waves and the resonance condition described by Vriend et al. [2007]. The waveguide model still holds in the dune for the observed velocities, even with a velocity increase with depth as implied by Andreotti et al. [2008]. Secondly, the method of initiation of spontaneous avalanching does not influence the booming frequency. The frequency is independent of the source once sustained booming starts; it depends on the subsurface structure of the dune. Thirdly, if all data points from Vriend et al. [2007] are included in the analysis (and not an average or selection), no correlation is observed between the sustained booming frequency and average particle diameter

The effect of material cyclic deformation properties on residual stress generation by laser shock processing

Laser shock processing (LSP) is a mechanical surface treatment to induce a compressive residual stress state into the near surface region of a metallic component. The effect of the cyclic deformation properties of ductile materials on the final residual stress fields obtained by LSP is analysed. Conventional modelling approaches either use simple tensile yield criteria, or isotropic hardening models if cyclic straining response is considered for the material during the peen processing. In LSP, the material is likely to be subject to cyclic loading because of reverse yielding after the initial plastic deformation. The combination of experiment and modelling shows that the incorporation of experimentally-determined cyclic stress-strain data, including mechanical hysteresis, into material deformation models is required to correctly reflect the cyclic deformation processes during LSP treatment and obtain accurate predictions of the induced residual stresses.</p

Optimización de los parámetros de operación en un proceso de tratamiento de aguas por electro-oxidación

En este estudio se evaluó la electro-oxidación como tratamiento para aguas residuales provenientes del proceso de producción de resinas fenólicas. Los experimentos se llevaron a cabo en un reactor tipo batch a escala laboratorio con una configuración monopolar con electrodos de grafito y titanio. Se realizaron ensayos preliminares con un volumen de muestra de 200 ml, un área sumergida de 25.13 cm2 para el electrodo de grafito (ánodo) y 40 cm2 para el electrodo de titanio (cátodo) y un tiempo de residencia de 240 minutos, 15 voltios y una agitación de 200 rpm.113 p.This study evaluated the electro-oxidation of phenolic resins production wastewater treatment. The experiments were carried out in a laboratory scale batch reactor with a monopolar configuration was built with graphite (anode) and titanium (cathode) electrodes. Prelimary tests were carried out with a sample volume of 200 ml, a submerged area of 25.13 cm2 for the graphite electrode and 40 cm2 for the titanium electrode and 240 minutes as a residence time, voltage of 15 V and an agitation value of 200 rpm.Contenido parcial: Aguas contaminadas con fenol -- Procesos electroquímicos de oxidación avanzada -- Electro-Oxidación -- Aspectos técnicos de operación de la electro-oxidación -- Especificaciones técnicas de la celda para electro-oxidación -- Diseño de experimentos

Infiltration Measurements for Soil Hydraulic Characterization

This book summarises the main results of many contributions from researchers worldwide who have used the water infiltration process to characterize soil in the field. Determining soil hydrodynamic properties is essential to interpret and simulate the hydrological processes of economic and environmental interest. This book can be used as a guide to soil hydraulic characterization and in addition it gives a complete description of the treated techniques, including an outline of the most significant research results, with the main points that still needing development and improvement

Solving the mystery of booming sand dunes

Desert booming can be heard after a natural slumping event or during a sand avalanche generated by humans sliding down the slip face of a large dune. The sound is remarkable because it is composed of one dominant audible frequency (70 to 105 Hz) plus several higher harmonics. This study challenges earlier reports that the dunes’ frequency is a function of average grain size by demonstrating through extensive field measurements that the booming frequency results from a natural waveguide associated with the dune. The booming frequency is fixed by the depth of the surficial layer of dry loose sand that is sandwiched between two regions of higher compressional body wave velocity. This letter presents measurements of the booming frequencies, compressional wave velocities, depth of surficial layer, along with an analytical prediction of the frequency based on constructive interference of propagating waves generated by avalanching along the dune surface

Dynamics of a structured slug population model in the absence of seasonal variation

We develop a novel, nonlinear structured population model for the slug Deroceras reticulatum, a highly significant agricultural pest of great economic impact, in both organic and non-organic settings. In the absence of seasonal variations, we numerically explore the effect of life history traits that are dependent on an individual's size and measures of population biomass. We conduct a systematic exploration of parameter space and highlight the main mechanisms and implications of model design. A major conclusion of this work is that strong size dependent predation significantly adjusts the competitive balance, leading to non-monotonic steady state solutions and slowly decaying transients consisting of distinct generational cycles. Furthermore, we demonstrate how a simple ratio of adult to juvenile biomass can act as a useful diagnostic to distinguish between predated and non-predated environments, and may be useful in agricultural settings