scholarly journals Time-lapse monitoring of fluid-induced geophysical property variations within an unstable earthwork using P-wave refraction

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. EN17-EN27 ◽  
Author(s):  
Paolo Bergamo ◽  
Ben Dashwood ◽  
Sebastian Uhlemann ◽  
Russell Swift ◽  
Jonathan E. Chambers ◽  
...  
Keyword(s):  
Time Lapse ◽  
P Wave ◽  
Data Sets ◽  
Time Intervals ◽  
Total Period ◽  
Seismic Properties ◽  
Wave Refraction ◽  
Regular Time ◽  
Spatial Locations ◽  
Spatial Regularization

A significant portion of the UK’s transportation system relies on a network of geotechnical earthworks (cuttings and embankments) that were constructed more than 100 years ago, whose stability is affected by the change in precipitation patterns experienced over the past few decades. The vulnerability of these structures requires a reliable, cost- and time-effective monitoring of their geomechanical condition. We have assessed the potential application of P-wave refraction for tracking the seasonal variations of seismic properties within an aged clay-filled railway embankment, located in southwest England. Seismic data were acquired repeatedly along the crest of the earthwork at regular time intervals, for a total period of 16 months. P-wave first-break times were picked from all available recorded traces, to obtain a set of hodocrones referenced to the same spatial locations, for various dates along the surveyed period of time. Traveltimes extracted from each acquisition were then compared to track the pattern of their temporal variability. The relevance of such variations over time was compared with the data experimental uncertainty. The multiple set of hodocrones was subsequently inverted using a tomographic approach, to retrieve a time-lapse model of [Formula: see text] for the embankment structure. To directly compare the reconstructed [Formula: see text] sections, identical initial models and spatial regularization were used for the inversion of all available data sets. A consistent temporal trend for P-wave traveltimes, and consequently for the reconstructed [Formula: see text] models, was identified. This pattern could be related to the seasonal distribution of precipitation and soil-water content measured on site.

Assessing the Validity of Near-Infrared Monochromator Calibrations over Time

1998 ◽  
Vol 52 (4) ◽  
pp. 604-612 ◽  
Author(s):  
Eric Bouveresse ◽  
Chiara Casolino ◽  
Désiré-Luc Massart
Keyword(s):  
Near Infrared ◽  
Calibration Model ◽  
Data Sets ◽  
Time Intervals ◽  
Regular Time ◽  
Calibration Models ◽  
Infrared Spectrometer ◽  
Near Infrared Spectrometer ◽  
Over Time ◽  
Infrared Data

A procedure to check the validity of near-infrared calibration models over time is proposed. Validation samples are analyzed at regular time intervals by both near-infrared and reference methods in order to check the validity of the near-infrared calibration model. When an invalid situation is detected, a stable polystyrene standard is measured, to determine whether this invalid situation is due to fluctuations of the instrumental response of the near-infrared spectrometer or not. A first method based on simulating simple instrumental differences enables one to correct those simple differences with only the polystyrene standard. It is shown that such an approach can correct most of the simple instrumental differences without the use of standardization procedures. However, when the invalid situation is due to more complex instrumental differences, standardization must be applied. This procedure is applied to simulated and real near-infrared data sets.

Sensitivity of Estimates of Seasonal Phytoplankton Photosynthesis to Sampling Frequency

1994 ◽  
Vol 51 (12) ◽  
pp. 2734-2738 ◽  
Author(s):  
E. U. Schindler ◽  
E. R. DeBruyn ◽  
E. J. Fee ◽  
J. A. Shearer
Keyword(s):  
Thermal Stratification ◽  
Sampling Frequency ◽  
Canadian Shield ◽  
Data Sets ◽  
Time Intervals ◽  
Rainfall Events ◽  
Northwestern Ontario ◽  
Regular Time ◽  
Sampling Intervals ◽  
Phytoplankton Photosynthesis

Phytoplankton photosynthesis was monitored once or twice weekly in an oligotrophic Canadian Shield lake in northwestern Ontario during the ice-free season for 6 yr. These data sets were subsampled in various ways to determine how the precision of estimates of ice-free season phytoplankton photosynthesis was affected by sampling frequency. Deviations were as large as 20% if a measurement was not taken before thermal stratification was established in the spring, or if samples were taken at monthly intervals during the ice-free season. Shorter sampling intervals (1, 2, and 3 wk were tested) all resulted in deviations of about 10%. Taking samples irregularly (every day for the 3 d subsequent to rainfall events ≥ 5 mm) instead of at regular time intervals did not reduce deviations.

scholarly journals Time-lapse anomalous X-ray diffraction shows how Fe2+substrate ions move through ferritin protein nanocages to oxidoreductase sites

2015 ◽  
Vol 71 (4) ◽  
pp. 941-953 ◽  
Author(s):  
Cecilia Pozzi ◽  
Flavio Di Pisa ◽  
Daniela Lalli ◽  
Camilla Rosa ◽  
Elizabeth Theil ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Rana Catesbeiana ◽  
Time Lapse ◽  
Data Sets ◽  
X Ray Diffraction ◽  
Ferrous Ions ◽  
Time Intervals ◽  
X Ray ◽  
Protein Cages ◽  
Aerobic And Anaerobic

Ferritin superfamily protein cages reversibly synthesize internal biominerals, Fe2O3·H2O. Fe2+and O2(or H2O2) substrates bind at oxidoreductase sites in the cage, initiating biomineral synthesis to concentrate iron and prevent potentially toxic reactions products from Fe2+and O2or H2O2chemistry. By freezing ferritin crystals ofRana catesbeianaferritin M (RcMf) at different time intervals after exposure to a ferrous salt, a series of high-resolution anomalous X-ray diffraction data sets were obtained that led to crystal structures that allowed the direct observation of ferrous ions entering, moving along and binding at enzyme sites in the protein cages. The ensemble of crystal structures from both aerobic and anaerobic conditions provides snapshots of the iron substrate bound at different cage locations that vary with time. The observed differential occupation of the two iron sites in the enzyme oxidoreductase centre (with Glu23 and Glu58, and with Glu58, His61 and Glu103 as ligands, respectively) and other iron-binding sites (with Glu53, His54, Glu57, Glu136 and Asp140 as ligands) reflects the approach of the Fe2+substrate and its progression before the enzymatic cycle 2Fe2++ O2→ Fe3+—O—O—Fe3+→ Fe3+—O(H)—Fe3+and turnover. The crystal structures also revealed different Fe2+coordination compounds bound to the ion channels located at the threefold and fourfold symmetry axes of the cage.

A rock-physics investigation of unconsolidated saline permafrost: P-wave properties from laboratory ultrasonic measurements

Geophysics ◽  
2016 ◽  
Vol 81 (1) ◽  
pp. WA233-WA245 ◽  
Author(s):  
Shan Dou ◽  
Seiji Nakagawa ◽  
Douglas Dreger ◽  
Jonathan Ajo-Franklin
Keyword(s):  
Wave Attenuation ◽  
Rock Physics ◽  
P Wave ◽  
Data Sets ◽  
Pore Scale ◽  
Seismic Properties ◽  
Rock Physics Modeling ◽  
Physics Modeling ◽  
Ice Content ◽  
Wave Properties

Saline permafrost is sensitive to thermal disturbances and is prone to subsidence, which renders it a major source of geohazard in Arctic coastal environments. Seismic methods could be used to map and monitor saline permafrost at scales of geotechnical interests because of the ice-content dependencies of seismic properties. We have developed a comprehensive study of the ultrasonic P-wave properties (i.e., velocity and attenuation) of synthetic saline permafrost samples for a range of salinities and temperatures, and measurements conducted on a fine-grained permafrost core obtained from Barrow, Alaska. The resulting data consist of P-wave properties presented as functions of temperature and salinity. Notable observations include the following: P-wave velocities showed marked reductions in the presence of dissolved salts and complex variations resulting from the water-to-ice phase transitions; strong P-wave attenuation was present in the temperature intervals in which the samples were partially frozen. When presented as functions of ice saturation, the data sets lead us to two key findings: (1) neither a purely cementing nor a purely pore-filling model of the pore-scale distributions of ice could adequately fit the observed velocity data and (2) although the velocities increase monotonically with increasing ice saturations, P-wave attenuation reaches a maximum at intermediate ice saturations—contrary to the ordinary expectation of decreasing attenuation with increasing velocities. The observed ice-content dependencies of P-wave properties, along with the implications on the probable pore-scale distributions of ice, provide a valuable basis for rock-physics modeling, which in turn could facilitate seismic characterizations of saline permafrost.

scholarly journals Imputation of confidential data sets with spatial locations using disease mapping models

2014 ◽  
Vol 33 (11) ◽  
pp. 1928-1945 ◽  
Author(s):  
Thais Paiva ◽  
Avishek Chakraborty ◽  
Jerry Reiter ◽  
Alan Gelfand
Keyword(s):  
Disease Mapping ◽  
Data Sets ◽  
Confidential Data ◽  
Spatial Locations ◽  
Mapping Models

scholarly journals Speech rhythm: a metaphor?

2014 ◽  
Vol 369 (1658) ◽  
pp. 20130396 ◽  
Author(s):  
Francis Nolan ◽  
Hae-Sung Jeon
Keyword(s):  
Traditional View ◽  
Time Intervals ◽  
Speech Rhythm ◽  
Linguistic Structure ◽  
Regular Time ◽  
Linguistic Functions ◽  
Absence Of Evidence ◽  
Metaphorical Extension ◽  
Analogical Process

Is speech rhythmic? In the absence of evidence for a traditional view that languages strive to coordinate either syllables or stress-feet with regular time intervals, we consider the alternative that languages exhibit contrastive rhythm subsisting merely in the alternation of stronger and weaker elements. This is initially plausible, particularly for languages with a steep ‘prominence gradient’, i.e. a large disparity between stronger and weaker elements; but we point out that alternation is poorly achieved even by a ‘stress-timed’ language such as English, and, historically, languages have conspicuously failed to adopt simple phonological remedies that would ensure alternation. Languages seem more concerned to allow ‘syntagmatic contrast’ between successive units and to use durational effects to support linguistic functions than to facilitate rhythm. Furthermore, some languages (e.g. Tamil, Korean) lack the lexical prominence which would most straightforwardly underpin prominence of alternation. We conclude that speech is not incontestibly rhythmic, and may even be antirhythmic. However, its linguistic structure and patterning allow the metaphorical extension of rhythm in varying degrees and in different ways depending on the language, and it is this analogical process which allows speech to be matched to external rhythms.

Processing and Excellent Oxidation Resistance of Nanocrystalline Fe-Cr Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 1122-1125
Author(s):  
Rajeev K. Gupta ◽  
B.V. Mahesh ◽  
R.K. Singh Raman ◽  
Carl C. Koch
Keyword(s):  
Oxidation Resistance ◽  
Secondary Ion Mass Spectrometry ◽  
Nanocrystalline Alloy ◽  
High Energy ◽  
Processing Route ◽  
Protective Oxide ◽  
Time Intervals ◽  
Regular Time ◽  
Order Of Magnitude ◽  
Energy Ball

Nanocrystalline and microcrystalline Fe-10Cr alloys were prepared by high energy ball milling followed by compaction and sintering, and then oxidized in air for 52 hours at 400°C. The oxidation resistance of nanocrystalline Fe-10Cr alloy as determined by measuring the weight gain after regular time intervals was compared with that of the microcrystalline alloy of same chemical composition (also prepared by the same processing route and oxidized under identical conditions). Oxidation resistance of nanocrystalline Fe10Cr alloy was found to be in excess of an order of magnitude superior than that of microcrystalline Fe10Cr alloy. The paper also presents results of secondary ion mass spectrometry of oxidized samples of nanocrystalline and microcrystalline Fe-Cr alloys, evidencing the formation of a more protective oxide scale in the nanocrystalline alloy.

Direct shear-wave seismic survey in Sanhu area, Qaidam Basin, west China

2022 ◽  
Vol 41 (1) ◽  
pp. 47-53
Author(s):  
Zhiwen Deng ◽  
Rui Zhang ◽  
Liang Gou ◽  
Shaohua Zhang ◽  
Yuanyuan Yue ◽  
...  
Keyword(s):  
Shear Wave ◽  
Reservoir Characterization ◽  
Qaidam Basin ◽  
P Wave ◽  
Data Sets ◽  
Direct Shear ◽  
Subsurface Structure ◽  
S Wave ◽  
West China ◽  
Wave Data

The formation containing shallow gas clouds poses a major challenge for conventional P-wave seismic surveys in the Sanhu area, Qaidam Basin, west China, as it dramatically attenuates seismic P-waves, resulting in high uncertainty in the subsurface structure and complexity in reservoir characterization. To address this issue, we proposed a workflow of direct shear-wave seismic (S-S) surveys. This is because the shear wave is not significantly affected by the pore fluid. Our workflow includes acquisition, processing, and interpretation in calibration with conventional P-wave seismic data to obtain improved subsurface structure images and reservoir characterization. To procure a good S-wave seismic image, several key techniques were applied: (1) a newly developed S-wave vibrator, one of the most powerful such vibrators in the world, was used to send a strong S-wave into the subsurface; (2) the acquired 9C S-S data sets initially were rotated into SH-SH and SV-SV components and subsequently were rotated into fast and slow S-wave components; and (3) a surface-wave inversion technique was applied to obtain the near-surface shear-wave velocity, used for static correction. As expected, the S-wave data were not affected by the gas clouds. This allowed us to map the subsurface structures with stronger confidence than with the P-wave data. Such S-wave data materialize into similar frequency spectra as P-wave data with a better signal-to-noise ratio. Seismic attributes were also applied to the S-wave data sets. This resulted in clearly visible geologic features that were invisible in the P-wave data.

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