scholarly journals Development and In Situ Application of Deformation Monitoring System for Concrete-Face Rockfill Dam Using Fiber Optic Gyroscope

Sensors ◽  
2019 ◽  
Vol 20 (1) ◽  
pp. 108
Author(s):  
Cheng Liao ◽  
Desuo Cai ◽  
Hongxun Chen ◽  
Weili Luo ◽  
Miao Li
Keyword(s):  
Monitoring System ◽  
Fiber Optic ◽  
Automatic Measurement ◽  
Deformation Monitoring ◽  
Fiber Optic Gyroscope ◽  
Distributed Monitoring ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Concrete Face

Deformation monitoring is of importance to ensure the operation status of concrete-face rockfill dams (CFRD). This paper reported a novel fiber optic gyroscope (FOG) monitoring system for continuously monitoring face slab deformation of CFRD, which consisted of a permanent monitoring pipeline and a sensing vehicle. The monitoring pipeline was made of steel pipes and polyvinyl chloride polymer connectors, which was embedded in a slot of the crushing-type sidewall beneath the concrete face slab of CFRD, forming a permanent monitoring channel. The sensing vehicle was equipped with a high-precision FOG sensor. A low-pass filter was designed to eliminate the vibration noise of the angular velocities of the sensing vehicle during the monitoring process. An in situ test was carried out on the Shuibuya dam, the highest CFRD in the world. The measurements of the FOG monitoring system agreed well with traditional instrument measurements, serving as validation of the system. The FOG monitoring system has the advantages of excellent repeatability, long service life, distributed monitoring, and automatic measurement.

Design of Fiber Distributed Busway Temperature Monitoring System

2013 ◽  
Vol 694-697 ◽  
pp. 1114-1117
Author(s):  
Yun Qin
Keyword(s):  
Monitoring System ◽  
Temperature Monitoring ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Arithmetic Average ◽  
Low Snr ◽  
Current State ◽  
Low Pass ◽  
Temperature Measurement System ◽  
Scattering Signal

The reliability of busway in high current state is closely related to its temperature. So effectively monitoring temperature is the key issue to ensure the busway work safely. Because of the constraints such as high voltage and strong electromagnetic fields, traditional temperature measurement system can not meet the requirements. A distributed busway temperature monitoring system is designed in this paper based on the temperature effect of fiber Raman scattering signal. Arithmetic average, wavelet noise reduction and low-pass filter combination of data processing is used to overcome the very low SNR. Experiments show that the system can measure the temperature of 1km busway effectively. Temperature resolution can achieve 3°C.

Assessment of wavelets analysis for carrier-phase multipath mitigationThis article is one of a series of papers published in this Special Issue on the theme GEODESY.

2009 ◽  
Vol 46 (8) ◽  
pp. 627-636
Author(s):  
Ahmed A. El-Ghazouly ◽  
Mohamed Elhabiby ◽  
Naser El-Sheimy
Keyword(s):  
Carrier Phase ◽  
Deformation Monitoring ◽  
Double Difference ◽  
Multipath Mitigation ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Adaptive Wavelet ◽  
Multipath Error ◽  
Phase Measurements ◽  
Search Volume

In carrier-phase measurements, which are the most precise observations for Global Positioning System (GPS) relative positioning, multipath error is still a factor that interferes with achieving the desired accuracy. Various improvements in receiver and antenna technologies, as well as modeling strategies, have resulted in better ways of coping with this error source. However, errors caused by multipath can be as large as 5 cm, which is not an acceptable accuracy, especially in precise surveying applications like deformation monitoring. In this paper, a full assessment of different wavelets techniques that can be used in multipath mitigation is made to evaluate the optimum way of using wavelets to reduce or remove this type of error. Also, a new approach based on the wavelet detrending technique is introduced to remove carrier-phase multipath error in the measurement domain. To mitigate multipath, GPS double-difference observables are fed to an adaptive wavelet analysis procedure based on high- and low-pass filter decomposition with different levels of resolution. Consequently, the observable sequences are corrected; these corrected observables can then be used to reduce the ambiguity search volume during the initial float solution stage. Meanwhile, double-difference observations with multipath mitigation offer an efficient method for obtaining a better baseline solution.

scholarly journals Local artifacts in ice core methane records caused by layered bubble trapping and in-situ production: a multi-site investigation

2016 ◽  
Author(s):  
R. H. Rhodes ◽  
X. Faïn ◽  
E. J. Brook ◽  
J. R. McConnell ◽  
O. J. Maselli ◽  
...  
Keyword(s):  
Transport Model ◽  
Accumulation Rate ◽  
Ice Core ◽  
Ice Cores ◽  
Analytical Techniques ◽  
Site Investigation ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Bubble Trapping

Abstract. Superimposed on the coherent and major atmospheric changes in trace gases revealed by ice core records, local high frequency, non-atmospheric features can now be resolved due to improvement s in resolution and precision of analytical techniques. These are signals that could not have survived the low-pass filter effect that firn diffusion exerts on the atmospheric history and therefore do not result from changes in the composition of the atmosphere at the surface of the ice sheet. Using continuous methane (CH4) records obtained from five polar ice cores, we characterize these non-atmospheric signals and explore their origin. Isolated samples, enriched in CH4 in the Tunu13 (Greenland) record are linked to the presence of melt layers. Melting can enrich the methane concentration due to preferential dissolution of methane relative to nitrogen, but we find that an additional in-situ process is required to generate the full magnitude of these anomalies. Furthermore, in the all ice cores studied there is evidence of reproducible, decimetre-scale CH4 variability. Through a series of tests, we demonstrate that this sign al is an artifact of layered bubble trapping in a heterogeneous-density firn column; we term this phenomenon ‘trapping noise’. The magnitude of CH4 trapping noise increases with atmospheric CH4 growth rate and seasonality of density contrasts, and decreases with accumulation rate. Firn air transport model simulations, accounting for layered bubble trapping, are in agreement with our empirical data. Significant annual periodicity is present in the CH4 variability of two Greenland ice cores, suggesting that layered gas trapping at these sites is controlled by regular, seasonal variations in the physical properties of the firn.

scholarly journals Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation

2016 ◽  
Vol 12 (4) ◽  
pp. 1061-1077 ◽  
Author(s):  
Rachael H. Rhodes ◽  
Xavier Faïn ◽  
Edward J. Brook ◽  
Joseph R. McConnell ◽  
Olivia J. Maselli ◽  
...  
Keyword(s):  
Growth Rate ◽  
High Frequency ◽  
Ice Core ◽  
Ice Cores ◽  
Gas Diffusion ◽  
Atmospheric Composition ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Bubble Trapping

Abstract. Advances in trace gas analysis allow localised, non-atmospheric features to be resolved in ice cores, superimposed on the coherent atmospheric signal. These high-frequency signals could not have survived the low-pass filter effect that gas diffusion in the firn exerts on the atmospheric history and therefore do not result from changes in the atmospheric composition at the ice sheet surface. Using continuous methane (CH4) records obtained from five polar ice cores, we characterise these non-atmospheric signals and explore their origin. Isolated samples, enriched in CH4 in the Tunu13 (Greenland) record are linked to the presence of melt layers. Melting can enrich the methane concentration due to a solubility effect, but we find that an additional in situ process is required to generate the full magnitude of these anomalies. Furthermore, in all the ice cores studied there is evidence of reproducible, decimetre-scale CH4 variability. Through a series of tests, we demonstrate that this is an artifact of layered bubble trapping in a heterogeneous-density firn column; we use the term “trapping signal” for this phenomenon. The peak-to-peak amplitude of the trapping signal is typically 5 ppb, but may exceed 40 ppb. Signal magnitude increases with atmospheric CH4 growth rate and seasonal density contrast, and decreases with accumulation rate. Significant annual periodicity is present in the CH4 variability of two Greenland ice cores, suggesting that layered gas trapping at these sites is controlled by regular, seasonal variations in the physical properties of the firn. Future analytical campaigns should anticipate high-frequency artifacts at high-melt ice core sites or during time periods with high atmospheric CH4 growth rate in order to avoid misinterpretation of such features as past changes in atmospheric composition.

scholarly journals Dynamics of Excitation and Inhibition in the Light-Adapted Limulus Eye in situ

1971 ◽  
Vol 58 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Marguerite Biederman-Thorson ◽  
John Thorson
Keyword(s):  
Steady State ◽  
Lateral Inhibition ◽  
Low Frequency ◽  
Dynamic Responses ◽  
Relaxation Processes ◽  
Pass Filter ◽  
Generator Potential ◽  
Low Pass Filter ◽  
Low Pass

The dynamics of spike discharge in eccentric cell axons from the in situ lateral eye of Limulus, under small sinusoidal modulation of light to which the eye is adapted, are described over two decades of light intensity and nearly three decades of frequency. Steady-state lateral inhibition coefficients, derived from the very low-frequency response, average 0.04 at three interommatidial spacings. The gain vs. frequency of a singly illuminated ommatidium is described closely from 0.004 to 0.4 cps by the linear transfer function s0.25; this function also accounts approximately for the measured phase leads, the small signal adaptation following small step inputs, and for Pinter's (1966) earlier low-frequency generator potential data. We suggest that such dynamics could arise from a summation in the generator potential of distributed intensity-dependent relaxation processes along the dendrite and rhabdome. Analysis of the dynamic responses of an eccentric cell with and without simultaneously modulated illumination of particular neighbors indicates an effect equivalent to self-inhibition acting via a first-order low-pass filter with time constant 0.42 sec, and steady-state gain near 4.0. The corresponding filters for lateral inhibition required time constants from 0.35 to 1 sec and effective finite delay of 50–90 msec.

scholarly journals Can We Use Satellite-Based Soil-Moisture Products at High Resolution to Investigate Land-Use Differences and Land–Atmosphere Interactions? A Case Study in the Savanna

2020 ◽  
Vol 12 (11) ◽  
pp. 1701
Author(s):  
Carlos Román-Cascón ◽  
Marie Lothon ◽  
Fabienne Lohou ◽  
Nitu Ojha ◽  
Olivier Merlin ◽  
...  
Keyword(s):  
Land Use ◽  
Soil Moisture ◽  
High Resolution ◽  
Satellite Data ◽  
Tree Cover ◽  
Optical Data ◽  
Pass Filter ◽  
Low Pass Filter ◽  
In Situ Data

The use of soil moisture (SM) measurements from satellites has grown in recent years, fostering the development of new products at high resolution. This opens the possibility of using them for certain applications that were normally carried out using in situ data. We investigated this hypothesis through two main analyses using two high-resolution satellite-based soil moisture (SBSM) products that combined microwave with thermal and optical data: (1) The Disaggregation based on Physical And Theoretical scale Change (DISPATCH) and, (2) The Soil Moisture Ocean Salinity-Barcelona Expert Center (SMOS-BEC Level 4). We used these products to analyse the SM differences among pixels with contrasting vegetation. This was done through the comparison of the SM measurements from satellites and the measurements simulated with a simple antecedent precipitation index (API) model, which did not account for the surface characteristics. Subsequently, the deviation of the SM from satellite with respect to the API model (bias) was analysed and compared for contrasting land use categories. We hypothesised that the differences in the biases of the varied categories could provide information regarding the water retention capacity associated with each type of vegetation. From the satellite measurements, we determined how the SM depended on the tree cover, i.e., the denser the tree cover, the higher the SM. However, in winter periods with light rain events, the tree canopy could dampen the moistening of the soil through interception and conducted higher SM in the open areas. This evolution of the SM differences that depended on the characteristics of each season was observed both from satellite and from in situ measurements taken beneath a tree and in grass on the savanna landscape. The agreement between both types of measurements highlighted the potential of the SBSM products to investigate the SM of each type of vegetation. We found that the results were clearer for DISPATCH, whose data was not smoothed spatially as it was in SMOS-BEC. We also tested whether the relationships between SM and evapotranspiration could be investigated using satellite data. The answer to this question was also positive but required removing the unrealistic high-frequency SM oscillations from the satellite data using a low pass filter. This improved the performance scores of the products and the agreement with the results from the in situ data. These results demonstrated the possibility of using SM data from satellites to substitute ground measurements for the study of land–atmosphere interactions, which encourages efforts to improve the quality and resolution of these measurements.

Novel mechanical antialiasing fiber-optic hydrophone with a fourth-order acoustic low-pass filter

2008 ◽  
Vol 33 (11) ◽  
pp. 1267 ◽  
Author(s):  
Zefeng Wang ◽  
Yongming Hu ◽  
Zhou Meng ◽  
Hong Luo ◽  
Ming Ni
Keyword(s):  
Fourth Order ◽  
Fiber Optic ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass
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