scholarly journals Long-term monitoring with spring-based gravimeters: tilt-control benefits and application to the Rochefort Cave Laboratory (Belgium)

2020 ◽  
Author(s):  
Benjamin Fores ◽  
Arnaud Watlet ◽  
Michel Van Camp ◽  
Olivier Francis
Keyword(s):  
Linear Drift ◽  
Term Stability ◽  
Long Term Stability ◽  
New Information ◽  
Non Linear ◽  
Long Term Monitoring ◽  
The One ◽  
Term Monitoring ◽  
Local Hydrology

<p>Spring-based gravimeters are light and easy to install, with a precision around 5 μGal/√Hz. However, they are still not used for long-term gravity monitoring. The main reason for that is the non-linear drift of those instruments, which is very difficult to correct without removing geophysical signals. We will show that when the tilt is actively controlled, a gPhone spring-based gravimeter shows a quasi-linear drift and can reach a long-term stability at the µGal level.</p><p>This allows experiments such as the one in the Rochefort Cave Laboratory (Belgium). Thanks to the size of the gPhone and its low facility requirements, a monitoring from inside a cave was possible. Coupled with another gravity monitoring at the surface, it reveals new information on the local hydrology of this karstic site.</p>

scholarly journals Retrieval of Sediment Fill Factor by Inversion of a Modified Hapke Model Applied to Sampled HCRF from Airborne and Satellite Imagery

2018 ◽  
Vol 10 (11) ◽  
pp. 1758 ◽  
Author(s):  
Rehman Eon ◽  
Charles Bachmann ◽  
Aaron Gerace
Keyword(s):  
Angular Dependence ◽  
Fill Factor ◽  
Single Scattering ◽  
Laboratory Setting ◽  
Spectral Signatures ◽  
Long Term Monitoring ◽  
The One ◽  
Term Monitoring ◽  
Sediment Fill

The physical properties of a medium such as density, grain size and surface roughness all influence the angular dependence of spectral signatures. Radiative transfer models, such as the one developed by Hapke, can relate the angular dependence of the reflectance to these geophysical variables. This paper focuses on extracting geophysical parameters, fill factor (decreasing porosity) and the single scattering albedo (SSA), through the inversion of a modified version of the Hapke model of airborne and space-borne imagery. The inversion methodology was validated through controlled experiments within a laboratory setting, where a good correlation (R 2 = 0.72) between the retrieved fill factor and the measured density was obtained. Using the same approach, we also retrieved the sediment fill factor and SSA from airborne data collected by the NASA G-LiHT system, and space-borne data observed by the NOAA GOES imager. The results from these studies provide a mechanism to understand geophysical characteristics of the terrain and may potentially be used for long-term monitoring of the dynamic dunes system.

scholarly journals Study of lifetime of Platinum Modified Metal Oxides Electrodes

2020 ◽  
Vol 14 (4) ◽  
pp. 1479-1488
Author(s):  
Lemeyonouin Aliou Guillaume Pohan ◽  
Ollo Kambiré ◽  
Mohamed Berté ◽  
Lassiné Ouattara
Keyword(s):  
Metal Oxides ◽  
Platinum Metal ◽  
Porous Structures ◽  
Term Stability ◽  
Long Term Stability ◽  
Physical Measurements ◽  
Platinum Coating ◽  
The One ◽  
A Current

Pt, IrO2, RuO2, Pt-IrO2 and Pt-RuO2 electrodes have been shown to be effective in their application in various fields. However, it is necessary to study their long-term stability. So, our objective is to prepare them and study their lifetime using intensiostatic measurement. Then they were prepared at 400 °C on titanium plates used as a substrate. Physical measurements (scanning electron microscopy) of these anodes revealed that their surface are rough and porous structures. Lifetime study was carried out in H2SO4 9 N and under a current density of 410 mA /cm2. The long-term stability of Pt improved when coupled to IrO2 in contrast to RuO2. From this study, the performance of the electrode was found to increase in the order: RuO2 < Pt-RuO2 < Pt < Pt-IrO2 < IrO2. For RuO2 and IrO2 pure electrodes, the deactivation would be due to the dissolution of precursors deposited on the titanium. For the Pt pure electrode, deactivation would be due to the detachment of platinum coating. The deactivation of the Pt-IrO2 and Pt-RuO2 electrode would be due, on the one hand to the platinum detachment from IrO2 or RuO2 and on the other hand to the metal oxides (IrO2 or RuO2) dissolution.Keywords: Electrodes, platinum, metal oxides, lifetime.

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