Heat flux measurement from thermal infrared imagery in low-flux fumarolic zones: Example of the Ty fault (La Soufrière de Guadeloupe)

International audienceMonitoring the geothermal flux of a dormant volcano is necessary both for hazard assessment and for studying hydrothermal systems. Heat from a magma body located at depth is transported by steam to the surface, where it is expelled in fumaroles if the heat flow exceeds 500 W/m2. If the heat flow is lower than 500 W/m2, steam mainly condensates in the soil close to surface and produces a thermal anomaly detectable at the surface. In this study, we propose a method to quantify low heat fluxes from temperature anomalies measured at the surface by a thermal infrared camera. Once corrected from the atmospheric and surface effects, thermal infrared images are used to compute (1) the excess of radiative flux, (2) the excess of sensible flux and (3) the steam flux from the soil to the atmosphere. These calculations require measurements of atmospheric parameters (temperature, wind velocity and humidity) and estimations of surface parameters (roughness and emissivity). This method has been tested on a low-flux fumarolic zone of the Soufrière volcano (Guadeloupe Island -- Lesser Antilles), and compared to a flux estimation realized from the thermal gradient measurements into the soil. The two methods show a good agreement and a similar precision (267 ± 46 W/m2 for the thermal infrared method, and 275 ± 50 W/m2 for the vertical temperature gradient method), if surface roughness is well calibrated

Du moderne en Corée: l'écriture, la colonisation, le destin

This study aims to elucidate in three stages how Western modernity has spread in South Korea. It opens first with a philological approach, emphasizing the gradual shift between using ideograms and an alphabet-based writing system. It then examines the impact of Japanese colonization. Lastly, the study concludes with the very translation of the concept of what “modern” means in Korean, focusing on political and cultural spheres. Cette étude vise à poser trois grands jalons pour comprendre comment la modernité occidentale a essaimé en Corée du Sud. Elle s’ouvre sur une première partie plus philologique, en prenant l’exemple du basculement progressif entre les idéogrammes et une écriture alphabétique. Elle questionne ensuite le rôle de la colonisation japonaise. Elle se conclut sur la traduction même du concept de « moderne » en coréen, notamment dans les sphères politique et culturelle

A two-dimensional effective stress framework for modelling whole-life soil strength changes due to pore pressure generation and dissipation, Part 2: Applications

publishedVersio

Exploring the limits of soft x-ray magnetic holography: Imaging magnetization reversal of buried interfaces (invited)

The following article appeared in Journal of Applied Physics 109.7 (2011): 07D357 and may be found at http://scitation.aip.org/content/aip/journal/jap/109/7/10.1063/1.3567035Only a very few experimental techniques can address the microscopic magnetization reversal behavior of the different magnetic layers in a multilayered system with element selectivity. We present an element-selective study of ferromagnetic (FM) [Co/Pt]n multilayers with perpendicular anisotropy exchange-coupled to antiferromagnetic (AFM) FeMn and IrMn films performed with a new experimental set-up developed for both soft x-ray spectroscopy and holography imaging purposes. The spectroscopy analysis allows the quantification of the unpinned (pinned) uncompensated AFM moments, providing direct evidence of its parallel (antiparallel) alignment with respect to the FM moments. The holography experiments give a direct view of both FM and uncompensated AFM magnetic structures, showing that they replicate to each other during magnetization reversal. Remarkably, we show magnetic images for effective thicknesses as small as one monolayer. Our results provide new microscopic insights into the exchange coupling phenomena and explore the sensitivity limits of these techniques. Future trends are also discussed.We acknowledge technical support by the ESRF staff R. Barrett, R. Homs-Regojo, T. Trenit, and G. Retout. A. B. acknowledges support through a Ramo´n y Cajal contract from the Spanish MICINN. This work was supported in part by the Spanish MICINN through Projects CSD2007-00010, and MAT2010-21822 and by Comunidad de Madrid through Project S2009/MAT-1726.Comunidad de Madrid. S2009/MAT-1726/NANOBIOMAGNE

OMAE2009-79934 JACK-UP INSTALLATION ON AN UNEVEN SEABED: RECOMMENDATIONS FROM MODEL TESTING IN OVERCONSOLIDATED CLAY

ABSTRACT This paper presents results of a laboratory testing program employing a reduced-scaled model of a three-legged jack-up to investigate the influence of an adjacent footprint on spudcan installation. This study focused on the installation of the full jack-up with a single leg located adjacent to a surface discontinuity. This contrasts previous studies that focused on the behavior of a single leg model and aims to account for the coupled interaction of the three legs and hull. The investigation was conducted using a 1:200 model scale jack-up designed to represent an average commonly used field jack-up. It was fully instrumented for leg bending and axial force measurement, and allowed unconstrained horizontal motion and rotation in the plane of foundation-footprint offset. Installation was performed at foundation-footprint centerline offsets of 0.75, 0.89, and 1.0 times the footprint diameter in overconsolidated kaolin clay adjacent to three different footprint types. The three footprint types -spudcan generated, a similarly shaped vertical walled auger generated, and shallow slope -were used to analyze separately the effect of shape and soil disturbance

An Experimental Study of the Embedment of a Dynamically Installed Anchor in Sand

This paper presents a novel dynamically installed anchor concept suitable for sand. The anchor, referred to as the DPAIII, uses a thin ‘blade-like’ design to reduce bearing resistance during penetration, and comprises a lower plate attached to an upper removable follower. The anchor is installed through the kinetic energy it gains during free-fall in water. After embedment, the upper follower is removed leaving the lower plate an-chor vertically embedded in the sand. This paper examines the embedment potential of the DPAIII through centrifuge tests conducted at 100 g in both loose and dense sand, using a model DPA III with different fol-lower masses, impacting the model sand bed at two different velocities. The centrifuge tests show promising results, with anchor tip embedment in the range of 0.9 to 2.2 times the lower plate length. The tip embed-ment is found to be a function of the soil relative density, anchor mass and impact velocity

Jetted helical anchors in sand:a torque reducing technique

Jetting is a proven technique for reducing installation force during pile installation, although it can lead to reduced axial and lateral capacity due to soil disturbance. This paper explores the innovative application of jetting to helical anchors, which are a promising, efficient and environmentally friendly foundation solution for anchoring floating renewable energy devices. A pilot campaign of centrifuge tests in sand was conducted to assess how varying jetting flow rates impact the installation torque and subsequent pull-out capacity. Results demonstrate that jetting can lower the installation torque required for helical anchors compared to non-jetted installation, with only a moderate reduction in ultimate tensile capacity. These proof-of-concept tests underscore the potential of jetted helical anchor installations as a solution to overcome high torque demands, thus enhancing the feasibility of helical anchors as reliable offshore anchoring solutions

Centrifuge modelling of active slide–pipeline loading in soft clay

Submarine slides are a significant hazard to the safe operation of pipelines in the proximity of continental slopes. This paper describes the results of a centrifuge testing programme aimed at studying the impact forces exerted by a submarine slide on an offshore pipeline. This was achieved by dragging a model pipe at varying velocities through fine-grained soil at various degrees of consolidation, hence exhibiting properties spanning from the fluid to the geotechnical domains, relevant to the state of submarine slide material. To simulate the high strain rates experienced by the soil while flowing around a pipe in the path of a submarine slide, tests were conducted at pipe–soil velocities of up to 4.2 m/s. The changing density and shear strength of the samples were back-calculated from T-bar penetrometer test results. A hybrid approach combining geotechnical and fluid-mechanics-based components of horizontal drag resistance was developed. This approach provides an improved method to link the density and strength of the slide material to the force applied on the pipe. Besides fitting the present observations, the method provides an improved reinterpretation of similar data from the literature

Wave Energy Converter Power Take-off for the Albany M4; Dry Test and Initial Deployment

Ocean wave energy is a plentiful resource. Over the past thirty years there have been many ingenious generation devices. However, none of the commercial startups have successfully competed with wind and solar, and little information about how devices performed is available in the public domain. In contrast, the motivation for the Albany M4 is to provide open-access design and operational data. The M4 is a moored, multi-float, attenuator platform with a reciprocating, rotary, electromechanical power-take-off. This paper presents results and lessons learned for the drivetrain, starting with factory acceptance tests in May 2023, dry tests from Sept 2023 and sea trials from Nov 2024. Weaknesses in angular position measurement have been the cause of setbacks at different stages of development. In contrast, the data acquisition system is performing well and the supercapacitor power smoothing is operating as planned. Despite concerns about gearbox durability, due to backlash and coupling problems, the reduced-scale platform has survived a six-month deployment, including a significant wave height of over 2 m, and generated up to an average power of approximately 2 kW over 20 min, with a peak power of over 20 kW

Helically embedded plate anchors for floating offshore wind:potential and proof of concept

Helical anchors are a promising solution for anchoring floating offshore wind turbines, offering high holding capacity relative to their dry weight and noiseless installation. However, practical challenges associated with potentially high torque requirements coupled with their relatively poor performance under lateral loading have hampered their uptake by the offshore industry. This paper introduces the Helically Embedded PLate Anchor (HEPLA), a new anchor concept that is installed as a screw pile but loaded as a plate anchor. Installation involves rotating and pushing the follower shaft to reach a target depth, after which the shaft is detached and retrieved for subsequent installations, leaving only the helical plate embedded in the seabed. Proof-of-concept experiments conducted in a geotechnical centrifuge in overconsolidated kaolin clay show that the HEPLA concept is feasible, practical, and results in behaviour that is consistent with conventional helical anchors. The results indicate that the HEPLA has the potential to be a cost-effective and viable alternative offshore anchoring system, requiring lower installation torque than a conventional helical anchor (as the shaft can be smaller), less overall steel as the follower shaft is reused across installations, and significant resistance under non-vertical loading