International Journal of Agricultural Research, Innovation and Technology (IJARIT)
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Equivalent Circuit Models for SAW Delay Line Sensors
No full textInternational audienceSurface acoustic wave (SAW) devices are widely used as high quality factor filters for telecommunications. In recent years they have been investigated as sensors, which calls for application-specific electronic systems that interact with them. To design such circuits, it is important to understand the peculiarities of the devices, which may be a barrier for system designers. In this work, we explore different models that can be simulated in any circuit simulation environment, facilitating the creation of systems that interact with SAW delay lines, devices in which a signal is delayed by a constant time between piezoelectric transducers. The equivalent circuits of acoustic delay lines can be divided in two categories: a lumped-element model, based on frequency-dependent impedances implemented through the Foster and Mittag-Leffler theorems, and a distributed-element model, based on transmission lines. We compare qualitative frequency and time-domain characteristics among these categories so their limitations are clear, with the lumped-element model not being usable in the time domain due to its singularity at the center frequency. We also describe the process of implementation to achieve the model, while proposing a simple circuit block that can be included to represent perturbations on the device, which allows adjusting of the model response to different perturbations. Our model is also suitable for tests in distinct liquid media, provided that the parallel capacitor is fitted accordingly to model the electromagnetic wave induced in the device
The Far Side of Mars: Two Distant Marsquakes Detected by InSight
No full textInternational audienceFor over three Earth years the Marsquake Service has been analyzing the data sent back from the Seismic Experiment for Interior Structure—the seismometer placed on the surface of Mars by NASA’s InSight lander. Although by October 2021, the Mars seismic catalog included 951 events, until recently all these events have been assessed as lying within a radius of 100° of InSight. Here we report two distant events that occurred within days of each other, located on the far side of Mars, giving us our first glimpse into Mars’ core shadow zone. The first event, recorded on 25 August 2021 (InSight sol 976), shows clear polarized arrivals that we interpret to be PP and SS phases at low frequencies and locates to Valles Marineris, 146° ± 7° from InSight. The second event, occurring on 18 September 2021 (sol 1000), has significantly more broadband energy with emergent PP and SS arrivals, and a weak phase arriving before PP that we interpret as Pdiff. Considering uncertain pick times and poorly constrained travel times for Pdiff, we estimate this event is at a distance between 107° and 147° from InSight. With magnitudes of Mw 4.2 and 4.1, respectively, these are the largest seismic events recorded so far on Mars
« Le vernaculaire comme outil dans le monde postmoderne » (Jérôme Meizoz, Écrire les mondes vernaculaires. Littérature, ethnologie et création sociale, Rimouski/Trois-Rivières, Tangence éditeur, coll. « Confluence », 2021, 978-2-925015-17-8, 153 p.) dans Acta fabula, volume 23, numéro 1, janvier 2022.
No full textThe tidal-thermal evolution of the Pluto-Charon system
No full textInternational audienceThe existence of subsurface oceans on the satellites of the giant planets and Trans-Neptunian objects has been predicted for some time. Liquid oceans on icy worlds, if present, exert a considerable influence on the dynamics of the ice-ocean system and, because of the astrobiological potential, represent an important objective for future missions to the outer solar system. The Pluto-Charon system is representative of an icy moon orbiting a dwarf planet that is believed to have formed from the remnants of a giant impact. The evolution of icy moons is primarily controlled by the mode and efficiency of heat transfer through the outer ice shell, which is influenced by the presence of impurities, by tidal dissipation in the ice shell, and by the radioactive element budget in the silicate core. Previous studies on the evolution of the Pluto-Charon system generally considered either only the thermal or the tidal evolution, and in the cases where both were considered, the important effect of the presence of impurities in the liquid oceans was not addressed. Here, we consider the joint tidal-thermal evolution of the Pluto-Charon system by combining a comprehensive tidal model that incorporates a viscoelastic description of the tidal response with a parameterized thermal convection model developed for icy worlds. This approach enables an extensive analysis of the conditions required for the formation and maintenance of subsurface liquid oceans up to the present. Our results show that because of relatively fast circularization and synchronization of the orbits of Pluto and Charon, tidal heating is only important during the early stages of evolution (<1 Myr). As part of our study, we test the sensitivity of our results to a number of parameters that pertain to the orbital and thermal history. In all the studied cases, oceans on Pluto are always predicted to remain liquid to the present, ranging in thickness from 40 km to 150-km, whereas oceans on Charon, while in-place for approximately 4 Gyr, have solidified. This is supported by New Horizons observations of primarily extensional faults on Pluto and both extensional and compressional faults on Charon
The hazards of unconfined pyroclastic density currents: A new synthesis and classification according to their deposits, dynamics, and thermal and impact characteristics
No full textInternational audiencePyroclastic density currents (PDCs) that escape their confining channels are among the most dangerous of volcanic hazards. These unconfined PDCs are capable of inundating inhabited areas that may be unprepared for these hazards, resulting in significant loss of life and damage to infrastructure. Despite their ability to cause serious impacts, unconfined PDCs have previously only been described for a limited number of specific case studies. Here, we carry out a broader comparative study that reviews the different types of unconfined PDCs, their deposits, dynamics and impacts, as well as the relationships between each element. Unconfined PDCs exist within a range of concentration, velocity and temperature: characteristics that are important in determining their impact. We define four end-member unconfined PDCs: 1. fast overspill flows, 2. slow overspill flows, 3. high-energy surges, and 4. low-energy detached surges (LEDS), and review characteristics and incidents of each from historical eruptions. These four end-members were all observed within the 2010 eruptive sequence of Merapi, Indonesia. We use this well-studied eruption as a case study, focusing on the villages of Bakalan (13 km south of the volcano) and Bronggang (14 km south of the volcano), which were impacted by slow overspill flows and LEDS, respectively. These two unconfined PDC types are the least described from previous volcanic eruptions, but during the 2010 Merapi eruption the overspill flows resulted in building destruction and the LEDS in significant loss of life. We discuss the dynamics and deposits of these unconfined PDCs, and the resultant impacts. We then use the lessons learned from the 2010 Merapi eruption to assess some of the impacts associated with the deadly 2018 Fuego, Guatemala eruption. Satellite imagery and media images supplementing fieldwork were used to determine the presence of both overspill flows and LEDS, which resulted in the loss of hundreds of lives and the destruction of hundreds of buildings in inundated areas within 9 km of the summit. By cataloguing unconfined PDC characteristics, dynamics and impacts, we aim to highlight the importance and value of accounting for such phenomena in emergency management and planning at active volcanoes
Les représentations sociales des pêcheurs mahorais sur les évolutions du littoral et le changement climatique
No full textPanorama Project MaOre fishermen's social representations on the evolutions of the coastline and climate change Project funded by the Mission for Transversal and Interdisciplinary Initiatives (MITI) CNRS (Climate Change Challenge AAP 2020) Principal investigator Miki MORI with the laboratory Praxiling UMR 5267 CNRS The PANORAMA was an exploratory study aimed at better understanding the social representations of the evolution of the coastal environment and the effects of climate change for Maore. By articulating and co-constructing different methodologies and scientific knowledge on climate change, the project was structured in three stages (April-October 2021): interviews people who practice fishing (PPP) in Mtsamboro village in Mayotte, mediation and the creation of mediation tools, and a participatory workshop. In the end, we conducted 34 interviews and 21 residents participated in the workshops. The interview grid was co-constructed by the research team. The workshops were also co-constructed by the researchers based on the first analyses of the interviews and tested with the inhabitants. Four themes were used to design the workshops: coral, sediment, toponymy, and the chronological and temporal timeline in relation to the history of Mayotte and prevailing changes in the climate and environment.Le projet PANORAMA a constitué une étude exploratoire ayant pour but de mieux comprendre les représentations des populations de Mayotte avec les évolutions de leur environnement côtier et les effets du changement climatique. En articulant et co-construisant différentes méthodologies et connaissances scientifiques sur le changement climatique, le projet a été structuré en trois étapes (avril – octobre 2021) : réalisation des enquêtes auprès des personnes qui pratiquent la pêche (PPP) dans un village de Mayotte au nord de l'île (Mtsamboro), un travail de médiation et de création des outils médiateurs et une journée d’ateliers participatifs regroupant une vingtaine d'habitants et une dizaine de chercheurs dialoguant ensemble sur le changement climatique et l’évolution du littoral de Mayotte.Au final, nous avons effectué 34 entretiens et 21 habitants ont participé aux ateliers. La grille de l’entretien a été co-construite par l’équipe de chercheurs. Les ateliers aussi ont été co-construits entre chercheurs à partir des premières analyses des entretiens et mis à l'épreuve avec les habitants. Quatre thématiques qui ont servi de supports à la conceptions d'ateliers (corail, sédiment, toponyme, frise chronologique)
Experimental study of chemical evolution and isotope fractionation of Cl and Br in pore water expelled during strong clay compaction
No full textInternational audienceIn sedimentary basins, clay compaction by burial can lead to fluid overpressure and is suspected to also generate fresh waters, but few geochemical tracers are available to assess this process both qualitatively and quantitatively. Our objective was to carry out experiments on the chemical - and halogen (Cl, Br) isotope evolutions of pore water expelled during clay compaction. For this, the smectite-rich bentonite MX80 and an illite-rich marl (Sainte-Suzanne) were equilibrated with ocean water. During two compaction experiments under high fluid pressure (45 MPa), mechanical stress (up to 150 MPa) and temperature (up to 150 °C), it was found that the chemistry and isotope behavior is considerably different between the swelling clay and the non-swelling clay.We saw a general decrease of the cat- and anion concentrations in the expelled water, for swelling clay while its concentration slightly increases in the remaining pore fluid. This was not the case for non-swelling clay. More freshening of the expelled water occurred during the compaction at higher temperature.We also observed a larger range of isotopic variation for Br (δ81Br from 0.9‰ up to 1.5‰) than for Cl (δ37Cl from −0.5‰ to −0.1‰) in the compaction experiments. During the compaction of illite-rich marl, no significant variation of Cl isotope (δ37Cl close to 0‰) was observed while the δ81Br value of the expelled water showed the same general increase (from 0.9‰ up to 1.5‰) as during the compaction of smectite-rich bentonite.We observed limited mineralogical transformations in terms of dissolution/precipitation processes. Therefore the surface chemistry of the clay in combination with decreasing porosity, in part, drive the anion and isotope evolution. We propose that significant retention of Cl and Br in the pore water of the compacted smectite-rich bentonite is indicative of ultrafiltration and that Cl and Br isotopes are promising tracers to consider when tracking the origin of low-salinity formation waters in sedimentary basins
Deep mass redistribution prior to the 2010 Mw 8.8 Maule (Chile) Earthquake revealed by GRACE satellite gravity
No full textInternational audienceSubduction zones megathrust faults constitute a considerable hazard as they produce most of the world's largest earthquakes. However, the role in megathrust earthquake generation exerted by deeper subduction processes remains poorly understood. Here, we analyze the 2003 – 2014 space-time variations of the Earth's gravity gradients derived from three datasets of GRACE geoid models over a large region surrounding the rupture zone of the Mw 8.8 Maule earthquake. In all these datasets, our analysis reveals a large-amplitude gravity gradient signal, progressively increasing in the three months before the earthquake, North of the epicentral area. We show that such signals are equivalent to a water storage decrease over 2 months and cannot be explained by hydrological sources nor artefacts, but rather find origin from mass redistributions within the solid Earth on the continental side of the subduction zone. These gravity gradient variations could be explained by an extensional deformation of the slab around 150-km depth along the Nazca Plate subduction direction, associated with large-scale fluid release. Furthermore, the lateral migration of the gravity signal towards the surface from a low coupling segment around North to the high coupling one in the South suggests that the Mw 8.8 earthquake may have originated from the propagation up to the trench of this deeper slab deformation. Our results highlight the importance of observations of the Earth's time-varying gravity field from satellites in order to probe slow mass redistributions in-depth major plate boundaries and provide new information on dynamic processes in the subduction system, essential to better understand the seismic cycle as a whole
Native hymenopteran parasitoids associated with fruit‐infesting flies in three plant formations and prospects for biological control in Western Burkina Faso, West Africa
No full textInternational audience1. In Western Burkina Faso, fruit flies (Diptera: Tephritidae) cause economic impacts.Damage on a mango can reach 100% in late varieties, and on shea fruits, the averageattack rate is 66.5%. Parasitoids offer natural biocontrol services, but the potential forthis in Burkina Faso remains unknown. 2. We performed a survey (2017–2019) in three plant formations (natural fallows n=6; agroforestry parks n=6 and mango orchards n=6) to determine the levels of parasitism of tephritid fruit fly pests. For this purpose, fruits from cultivated and wildfruit fly host plant species were sampled in these plant formations and incubated forinsects’ emergence. 3. In total, 1822 adults belonging to 7 parasitoid species were found. Fopius caudatus (Szépligeti) and Psyttalia concolor (Szépligeti) with 51.47% and 30.60% of the total of parasitoid adults emerged, respectively, were the most predominant. Parasitismrate varied according to host fruit species. Pupae recorded from Sarcocephalus latifolius and Vitellaria paradoxa were most parasitized (27.22%±3.96%) and (17.08%±2.37%), respectively, while those obtained from mangoes were the lessparasitized (3.73%±0.91%). 4. Mass rearing of F. caudatus and P. concolor, as well as habitat management, will contribute to the promotion of both, augmentation and conservation biological control
Investigation on four-port mono-capacitor circuit with high-pass negative group delay behavior
No full textInternational audienceMost of the negative group delay (NGD) circuit recent investigation were focused on the classes of lowpass and bandpass categories. Few research works are currently available in the literature on the typical high-pass (HP) NGD function. This paper introduces an original HP-NGD circuit theory of four-port passive topology constituted by a single lumped capacitor. The S-matrix equivalent model of the innovative topology is established from the admittance matrix. Then, the basic frequency analytical responses are expressed. Then, the GD model is derived in function of the capacitor. It was found analytically that the four-port mono-capacitor passive circuit is susceptible to behave originally as an unfamiliar HP-NGD function. An innovative HP-NGD analysis is explored in addition to the expression of synthesis design equation in function of the expected NGD cutoff frequency which is linked to NGD optimal value. The validity of the established HP-NGD circuit theory is verified with a proof of concept (POC). As expected, the HP-NGD behavior showing a good correlation between analytical model and simulation is obtained