scholarly journals Performance of three iGrav superconducting gravity meters before and after transport to remote monitoring sites

2020 ◽  
Vol 223 (2) ◽  
pp. 959-972
Author(s):  
Florian Schäfer ◽  
Philippe Jousset ◽  
Andreas Güntner ◽  
Kemal Erbas ◽  
Jacques Hinderer ◽  
...  
Keyword(s):  
Geothermal Field ◽  
Absolute Gravity ◽  
Absolute Calibration ◽  
Noise Levels ◽  
Before And After ◽  
Gravity Measurements ◽  
Superconducting Gravity ◽  
The Stability ◽  
Comparison Measurements

SUMMARY High spatial and temporal resolution of gravity observations allows quantifying and understanding mass changes in volcanoes, geothermal or other complex geosystems. For this purpose, accurate gravity meters are required. However, transport of the gravity meters to remote study areas may affect the instrument's performance. In this work, we analyse the continuous measurements of three iGrav superconducting gravity meters (iGrav006, iGrav015 and iGrav032), before and after transport between different monitoring sites. For 4 months, we performed comparison measurements in a gravimetric observatory (J9, Strasbourg) where the three iGravs were subjected to the same environmental conditions. Subsequently, we transported them to Þeistareykir, a remote geothermal field in North Iceland. We examine the stability of three instrumental parameters: the calibration factors, noise levels and drift behaviour. For determining the calibration factor of each instrument, we used three methods: First, we performed relative calibration using side-by-side measurements with an observatory gravity meter (iOSG023) at J9. Secondly, we performed absolute calibration by comparing iGrav data and absolute gravity measurements (FG5#206) at J9 and Þeistareykir. Thirdly, we also developed an alternative method, based on intercomparison between pairs of iGravs to check the stability of relative calibration before and after transport to Iceland. The results show that observed changes of the relative calibration factors by transport were less than or equal to 0.01 per cent. Instrumental noise levels were similar before and after transport, whereas periods of high environmental noise at the Icelandic site limited the stability of the absolute calibration measurements, with uncertainties above 0.64 per cent (6 nm s–2 V–1). The initial transient drift of the iGravs was monotonically decreasing and seemed to be unaffected by transport when the 4K operating temperatures were maintained. However, it turned out that this cold transport (at 4 K) or sensor preparation procedures before transport may cause a change in the long-term quasi-linear drift rates (e.g. iGrav015 and iGrav032) and they had to be determined again after transport by absolute gravity measurements.

Numerical Simulation on Deformation Features and Filling Efficiency of Channel Goaf Foundation

2013 ◽  
Vol 353-356 ◽  
pp. 3707-3712
Author(s):  
Zhi Dong Zhou ◽  
Hong Bo Zhang ◽  
Xiu Guang Song ◽  
Hong Ya Yue
Keyword(s):  
Numerical Simulation ◽  
Comparative Analysis ◽  
Comprehensive Analysis ◽  
Obvious Effect ◽  
Before And After ◽  
Check Gate ◽  
Deformation Features ◽  
Natural Foundation ◽  
The Stability

For analyzing and evaluating the deformation features of channel goaf foundation and its effect on superstructure, according to the foundation reinforcement engineering of Ji-Liang Channel Check Gate, the comparative analysis on the differential settlement between the unfavorable foundation and natural foundation was performed by numerical simulation with FLAC3D. The computer results showed that the present foundation had obvious effect on the stability and security of the superstructure, so the engineering treatment are needed. Based on technical-economic comprehensive analysis among three treatment methods for strengthening the channel golf foundation with different kinds of filling, the reasonable method is put forward in this paper. By comparing mechanical characteristic of flashboard in channel goaf before and after strengthening, we confirmed the foundation stability of channel goaf and the security of the ground building which can satisfy the long term usage requirements.

Development and Assembly of a MEMS Based High-Sensitivity Relative Gravimeter for Multi-Pixel Imaging Applications 

2021 ◽  
Author(s):  
Karl Toland ◽  
Abhinav Prasad ◽  
Andreas Noack ◽  
Kristian Anastasiou ◽  
Richard Middlemiss ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Cost Effective ◽  
Mount Etna ◽  
Earth Tides ◽  
Gravity Measurements ◽  
Stepper Motors ◽  
Long Term Monitoring ◽  
The Stability ◽  
Term Monitoring

<p>The manufacture and production of a high-sensitivity cost-effective gravimeter has the potential to change the methodology and efficiency of gravity measurements. Currently, the most common method to conduct a survey is by using a single gravimeter, usually costing tens of thousands of Dollars, with measurements taken at multiple locations to obtain the required data. The availability of a cost-effective gravimeter however would allow the user to install multiple gravimeters, at the same cost of a single gravimeter, to increase the efficiency of surveys and long-term monitoring.  </p><p> </p><p>Since the previous reporting on a low-drift relative MEMS gravimeter for multi-pixel imaging applications (Prasad, A. et al, EGU2020-18528), significant progress has been made in the development and assembly of the previously reported system. Field prototypes have been manufactured and undergone significant testing to investigate the stability and robustness of the system in preparation for the deployment of multiple devices as part of the gravity imager on Mount Etna. The device, known as Wee-g, has several key features which makes it an attractive prospect in the field of gravimetry. Examples of these features are that the Wee-g is small and portable with the ability to connect to the device remotely, can be powered through a mains connected power supply, or through portable batteries, weighs under 4kg, has a low power consumption during normal use of 5W, correct for tilt through manual adjustments or remotely through integrated stepper motors with a total tilt correction range of 5 degrees, the ability to read out tilt of the device through an inclinometer for either alignment or long term monitoring and numerous temperature sensors and heater servos to control the temperature of the MEMS to <1mK.</p><p> </p><p>This presentation aims to report on the progress that has been achieved in the development and manufacturing of the prototype devices, various testing of the devices under various laboratory conditions (such as the measurements of the Earth tides, and a relative measurement of gravity at various floor levels), as well as additional applications that are to be explored in 2021. </p>

The Effect of VikaneTm on the Stability of Cellulosic and Ligneous Materials -- Measurement of Deterioration by Chemical and Physical Methods

1990 ◽  
Vol 185 ◽  
Author(s):  
Helen D. Burgess ◽  
Nancy E. Binnie
Keyword(s):  
Hydrolytic Degradation ◽  
Degree Of Polymerization ◽  
Accelerated Ageing ◽  
Total Acid ◽  
Long Term Stability ◽  
Before And After ◽  
Pulp Fibres ◽  
General Scientific ◽  
The Stability

AbstractVikaneTM (sulphuryl fluoride) is a commercial fumigant[1] which is used for the control of pests in museum collections. This paper summarizes the results obtained through an investigation of the effect of VikaneTM on twenty-five paper and textile samples. Samples chosen were representative of artifacts present in North American collections (cotton, linen, jute, and wood pulp fibres, from 1622 to present).The effect of the fumigation treatment has been evaluated by chemical and physical analyses: (1) Acidity -- surface pH, cold extracted pH, total acid (iodometric titration), (2) Oxidative and Hydrolytic Degradation - viscometric average degree of polymerization, carbonyl content (hydrazone derivatization), (3) and Fumigant Residues (specific ion electrode). Analysis of unfumigated and fumigated samples was carried out before and after accelerated ageing (70°C and 50% relative humidity) in order to estimate the long term stability of fumigated samples.The data obtained show that commercial grade VikaneTM degrades cellulosic and ligneous fibres. A second set of experiments on two fibre types using a new experimental grade of VikaneTM gave significantly less degradation. The presentation of this work will concentrate upon a general scientific interpretation of results.It is anticipated that the conclusions will be applicable to a broad range of artifacts.

Geothermal reservoir monitoring with a combination of absolute and relative gravimetry

Geophysics ◽  
2008 ◽  
Vol 73 (6) ◽  
pp. WA37-WA47 ◽  
Author(s):  
Mituhiko Sugihara ◽  
Tsuneo Ishido
Keyword(s):  
History Matching ◽  
Observation Interval ◽  
Time Lapse ◽  
Gravity Measurement ◽  
Absolute Gravity ◽  
Short Term ◽  
Well Production ◽  
Gravity Measurements ◽  
Central Production

Microgravity monitoring is a valuable tool for mapping the redistribution of subsurface mass and for assessing changes in fluid recharge from reservoir boundaries associated with geothermal exploitation. To further the development of a high-precision absolute/relative hybrid gravity-measurement technique, we conducted measurements using an absolute gravimeter in two geothermal fields in Japan. The absolute gravity measurements were performed in the central production areas to directly measure gravity changes caused by fluid withdrawal. We succeeded in measuring long-term trends within an accuracy of a few microgals in the Okuaizu and Ogiri fields, which have been producing electricity for several years. Absolute measurements in the center of the field provide reliable and local reference datum anchor points for more widely distributed relative gravity measurements. In the Ogiri field, we carried out time-lapse hybrid measurements with this combination of absolute and relative gravimetry and delineated the spatial distributions of long- and short-term changes. The long-term changes are relatively small, considering the four-year observation interval. This suggests a near balance between the mass withdrawal rate from wells and mass recharge from peripheral regions. The apparent balance is reproduced fairly well by a preliminary numerical reservoir simulation study. The observed long- and short-term changes are thought to be useful constraints for planned history-matching studies based on refined reservoir models with greater spatial resolution that incorporate detailed well-by-well production histories.

Study on Stability of Dayantang Landslide under the Engineering Disturbance and Rainfall

2012 ◽  
Vol 594-597 ◽  
pp. 415-418
Author(s):  
Jian Jun Zhou ◽  
Hua Deng ◽  
Hao Peng
Keyword(s):  
Steady State ◽  
Anthropogenic Disturbance ◽  
Safety Monitoring ◽  
Numerical Results ◽  
Long Period ◽  
Unstable Failure ◽  
Before And After ◽  
Project Construction ◽  
The Stability

Dayantang slope was stable before Shuibuya project construction. Based on the long-term safety monitoring, it has appeared the obvious deformation during the project construction. According the monitoring datas, the stability of the landslide before and after the construction was discussed and analyzed. Considering the rainfall effect on landslide after it has been strongly anthropogenic disturbance, the numerical results show that it is in critical steady state without rainfall, while get worse and even unstable failure under the influence of the intensive rain and the long period of rainfall.

Gravity changes before and after the 2015 Mw7.8 Nepal earthquake

2020 ◽  
Author(s):  
Weimin Xu ◽  
Shi Chen ◽  
Hongyan Lu
Keyword(s):  
Source Region ◽  
Absolute Gravity ◽  
Nepal Earthquake ◽  
Source Regions ◽  
Gravity Changes ◽  
Seismogenic Source ◽  
Before And After ◽  
Gravity Measurements ◽  
The Absolute ◽  
Regional Gravity

<p>Based on the absolute gravity measurements of 4 gravimetric stations (Shigatse, Zhongba, Lhasa and Naqu) in southern Tibet surveyed from 2010 to 2013, we modeled the source region as a disk of 580 km in diameter by Hypocentroid model, shown that the gravity increase at these stations may be related to mass changes in the source region of the 2015 Mw7.8 Nepal earthquake. We analyzed the characteristics of gravity variations from the repeated regional gravity network, which including the 4 absolute gravimetric stations and 13 relative gravimetric stations from 2010 to 2019, to study the characteristics of gravity changes before and after the earthquake.</p><p>We firstly estimated the reliability of the absolute gravity measurements by the errors of each station, and considered the effect of vertical displacement, denudation of surface mass, GIA correction and the secular and background gravity changes. Secondly we employed the Bayesian adjustment method for the relative gravimetric network data analysis, which was more robust and adaptive for solving problems caused by irregular nonlinear drift of different gravimeters, and then carried out error analysis for the repeated relative gravity measurements. Furthermore, we took the Shigatse station as example, which covered absolute and relative measurements and was most close to the Hypocenter of the inversion Hypocentroid model, the hydrologic effects of the Shigatse station was modeled exactly, and the results shown that the secular and background gravity changes were much smaller than the observed gravity changes. Lastly we studied the characteristics of gravity changes before and after the earthquake through the Hypocentroid model, we found the coincident gravity increase both in absolute and repeated regional gravity results before the earthquake, and gravity decreased after the earthquake, which suggested that the pre-earthquake gravity increase may be caused by strain and mass (fluid) transfer in broad seismogenic source regions of the earthquake. Moreover, the study indicated that high-precision ground gravity measurements (absolute and relative) may provide a useful method for monitoring mass changes in the source regions of potential large earthquakes.</p><p> </p><p><strong>Acknowledgment: </strong>This research is supported by National Key R&D Program of China (Grant No.2018YFC1503806 and No.2017YFC1500503) and National Natural Science Foundation of China (Grant No.U1939205 and No.41774090).</p>

scholarly journals The effect of Natura 2000 network on the Eurasian Eagle-owl (Bubo bubo) population in Southeast Bulgaria: implications for conservation

2021 ◽  
Vol 29 (1) ◽  
pp. 170-178
Author(s):  
Boyan Milchev ◽  
Valeri Georgiev
Keyword(s):  
Gap Analysis ◽  
Natura 2000 ◽  
Area Network ◽  
Bubo Bubo ◽  
Long Term Study ◽  
Before And After ◽  
Eagle Owl ◽  
The Stability ◽  
Special Protection Areas

Abstract The effectiveness and efficiency of the Natura 2000 network for the Eurasian Eagle-owl conservation in SE Bulgaria was assessed by comparing data collected during a long-term study on number of breeding pairs and fledglings before and after network establishment. The Natura 2000 network and non-protected areas showed similar values of the calculated indices according to the number of occupied localities. However, the pairs in Natura 2000 sites bred significantly less fledglings after the creation of the network than the pairs in non-protected ones. The Special Protection Areas (SPA) system created specifically for the preservation of birds has the lowest efficiency in respect to Eurasian Eagle-owl protection. Proposals were made after ‘gap analysis’ for real protection and optimization of the protected-area network to increase the stability of the Eurasian Eagle-owl population in the changing environment.

scholarly journals Thirty years of precise gravity measurements at Mt. Vesuvius: an approach to detect underground mass movements

2013 ◽  
Vol 56 (4) ◽  
Author(s):  
Giovanna Berrino ◽  
Vincenzo d’Errico ◽  
Giuseppe Ricciardi
Keyword(s):  
Ground Deformation ◽  
Reference Station ◽  
Absolute Gravity ◽  
Volcanic Area ◽  
Gravity Station ◽  
Gravity Changes ◽  
Gravity Measurements ◽  
Elevation Changes ◽  
Gravity Network

<p>Since 1982, high precision gravity measurements have been routinely carried out on Mt. Vesuvius. The gravity network consists of selected sites most of them coinciding with, or very close to, leveling benchmarks to remove the effect of the elevation changes from gravity variations. The reference station is located in Napoli, outside the volcanic area. Since 1986, absolute gravity measurements have been periodically made on a station on Mt. Vesuvius, close to a permanent gravity station established in 1987, and at the reference in Napoli. The results of the gravity measurements since 1982 are presented and discussed. Moderate gravity changes on short-time were generally observed. On long-term significant gravity changes occurred and the overall fields displayed well defined patterns. Several periods of evolution may be recognized. Gravity changes revealed by the relative surveys have been confirmed by repeated absolute measurements, which also confirmed the long-term stability of the reference site. The gravity changes over the recognized periods appear correlated with the seismic crises and with changes of the tidal parameters obtained by continuous measurements. The absence of significant ground deformation implies masses redistribution, essentially density changes without significant volume changes, such as fluids migration at the depth of the seismic foci, i.e. at a few kilometers. The fluid migration may occur through pre-existing geological structures, as also suggested by hydrological studies, and/or through new fractures generated by seismic activity. This interpretation is supported by the analyses of the spatial gravity changes overlapping the most significant and recent seismic crises.</p>

scholarly journals Enterococci Isolated from Japanese Quails Exposed to Microgravity Conditions and Stability of their Properties

2009 ◽  
Vol 78 (2) ◽  
pp. 253-258 ◽  
Author(s):  
Andrea Lauková ◽  
Gabriela Michlovičová
Keyword(s):  
Lactic Acid Production ◽  
Long Term Storage ◽  
Japanese Quails ◽  
Before And After ◽  
Long Time ◽  
Microgravity Conditions ◽  
The Stability ◽  
Enterocin A ◽  
Long Storage

Enterococci isolated from the crop and caecum of Japanese quails exposed to 7 day conditions of microgravity were re-vitalized after their dry-freezing long storage. Originally, the strains were isolated from Japanese quails after their landing from flight onboard the orbital station Mir during the experiment in August 1990. Because taxonomy as well as the studies concerning the bacteriocins, especially those produced by enterococci, have been continually developed for years, the aim of this study was to confirm species identification, stability of the properties of enterococci as well as to test new properties after their long storage. Genotyping allotted the strains to the species E. faecium. Lactic acid production was detected in similar amounts in the strains before and after their long-storage in dry-frozen form. The strains were vancomycinsensitive and kanamycin-resistant before as well as after their long-time storage. Variability in sensitivity to different antibiotics was found among the strains tested even before and after longtime storage. Each of the strains possessed at least one structural enterocin gene. The structural genes for enterocin A, P, B, L50B were detected in E. faecium EP7. E. faecium EP2, EEP4 have the genes for ent A, B, L50B. The gene for ent P was detected only in the strain EP7. The most often detected was ent A gene followed by ent genes B, L50B. All strains inhibited growth of at least 4 out of 15 indicators. The stability of the enterococcal properties determined before as well as after their dry-freezing was not influenced during their long-term storage; moreover, new properties were determined.

The stability of dislocation networks under various oxygen-doping conditions in superconducting Bi2Sr2CaCu2Oy single crystals and their influence on the flux pinning properties

1994 ◽  
Vol 52 ◽  
pp. 802-803
Author(s):  
Y. Feng ◽  
X. Y. Cai ◽  
R. J. Kelley ◽  
D. C. Larbalestier
Keyword(s):  
Single Crystals ◽  
Oxygen Content ◽  
Basal Plane ◽  
Flux Pinning ◽  
Pinning Centers ◽  
Before And After ◽  
Anomalous Peak ◽  
Basal Plane Dislocation ◽  
The Stability ◽  
Further Development

The issue of strong flux pinning is crucial to the further development of high critical current density Bi-Sr-Ca-Cu-O (BSCCO) superconductors in conductor-like applications, yet the pinning mechanisms are still much debated. Anomalous peaks in the M-H (magnetization vs. magnetic field) loops are commonly observed in Bi2Sr2CaCu2Oy (Bi-2212) single crystals. Oxygen vacancies may be effective flux pinning centers in BSCCO, as has been found in YBCO. However, it has also been proposed that basal-plane dislocation networks also act as effective pinning centers. Yang et al. proposed that the characteristic scale of the basal-plane dislocation networksmay strongly depend on oxygen content and the anomalous peak in the M-H loop at ˜20-30K may be due tothe flux pinning of decoupled two-dimensional pancake vortices by the dislocation networks. In light of this, we have performed an insitu observation on the dislocation networks precisely at the same region before and after annealing in air, vacuumand oxygen, in order to verify whether the dislocation networks change with varying oxygen content Inall cases, we have not found any noticeable changes in dislocation structure, regardless of the drastic changes in Tc and the anomalous magnetization. Therefore, it does not appear that the anomalous peak in the M-H loops is controlled by the basal-plane dislocation networks.

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