Estimating nitrate retention in a large constructed wetland using high-frequency, continuous monitoring and hydrologic modeling

2017 ◽  
Author(s):  
Chad W Drake ◽  
Christopher S Jones ◽  
Keith E Schilling ◽  
Antonio Arenas Amado ◽  
Larry J Weber
Keyword(s):  
Constructed Wetland ◽  
High Frequency ◽  
Continuous Monitoring ◽  
Hydrologic Modeling ◽  
Nitrate Retention

Estimating nitrate retention in a large constructed wetland using high-frequency, continuous monitoring and hydrologic modeling

2017 ◽  
Author(s):  
Chad W Drake ◽  
Christopher S Jones ◽  
Keith E Schilling ◽  
Antonio Arenas Amado ◽  
Larry J Weber
Keyword(s):  
Constructed Wetland ◽  
High Frequency ◽  
Continuous Monitoring ◽  
Hydrologic Modeling ◽  
Nitrate Retention

High-Frequency Continuous Monitoring to Track Vapor Intrusion Resulting From Naturally Occurring Pressure Dynamics

2017 ◽  
Vol 27 (2) ◽  
pp. 9-25 ◽  
Author(s):  
Vitthal Hosangadi ◽  
Brandon Shaver ◽  
Blayne Hartman ◽  
Michael Pound ◽  
Mark L. Kram ◽  
...  
Keyword(s):  
High Frequency ◽  
Continuous Monitoring ◽  
Vapor Intrusion ◽  
Naturally Occurring ◽  
Pressure Dynamics

scholarly journals Continuous Monitoring of Differential Reflectivity Bias for C-Band Polarimetric Radar Using Online Solar Echoes in Volume Scans

2019 ◽  
Vol 11 (22) ◽  
pp. 2714
Author(s):  
Chu ◽  
Liu ◽  
Zhang ◽  
Kou ◽  
Li
Keyword(s):  
High Frequency ◽  
Continuous Monitoring ◽  
Information Science ◽  
Elevation Angle ◽  
Gaussian Model ◽  
Likelihood Estimation ◽  
Polarimetric Radar ◽  
Time Calibration ◽  
Calibration Methods ◽  
Differential Reflectivity

The measurement error of differential reflectivity (ZDR), especially systematic ZDR bias, is a fundamental issue for the application of polarimetric radar data. Several calibration methods have been proposed and applied to correct ZDR bias. However, recent studies have shown that ZDR bias is time-dependent and can be significantly different on two adjacent days. This means that the frequent monitoring of ZDR bias is necessary, which is difficult to achieve with existing methods. As radar sensitivity has gradually been enhanced, large amounts of online solar echoes have begun to be observed in volume-scan data. Online solar echoes have a high frequency, and a known theoretical value of ZDR (0 dB) could thus allow the continuous monitoring of ZDR bias. However, online solar echoes are also affected by low signal-to-noise ratio and precipitation attenuation for short-wavelength radar. In order to understand the variation of ZDR bias in a C-band polarimetric radar at the Nanjing University of Information Science and Technology (NUIST-CDP), we analyzed the characteristics of online solar echoes from this radar, including the daily frequency of occurrence, the distribution along the radial direction, precipitation attenuation, and fluctuation caused by noise. Then, an automatic method based on online solar echoes was proposed to monitor the daily ZDR bias of the NUIST-CDP. In the proposed method, a one-way differential attenuation correction for solar echoes and a maximum likelihood estimation using a Gaussian model were designed to estimate the optimal daily ZDR bias. The analysis of three months of data from the NUIST-CDP showed the following: (1) Online solar echoes occurred very frequently regardless of precipitation. Under the volume-scan mode, the average number of occurrences was 15 per day and the minimum number was seven. This high frequency could meet the requirements of continuous monitoring of the daily ZDR bias under precipitation and no-rain conditions. (2) The result from the proposed online solar method was significantly linearly correlated with that from the vertical pointing method (observation at an elevation angle of 90°), with a correlation coefficient of 0.61, suggesting that the proposed method is feasible. (3) The day-to-day variation in the ZDR bias was relatively large, and 32% of such variations exceeded 0.2 dB, meaning that a one-time calibration was not representative in time. Accordingly, continuous calibration will be necessary. (4) The ZDR bias was found to be largely influenced by the ambient temperature, with a large negative correlation between the ZDR bias and the temperature.

Continuous Monitoring of Smith Shocks after Lubrication Failure

1995 ◽  
Vol 209 (1) ◽  
pp. 17-27
Author(s):  
J D Smith
Keyword(s):  
Condition Monitoring ◽  
High Frequency ◽  
Continuous Monitoring ◽  
Computer Memory ◽  
Test Technique ◽  
Pressure Pulses ◽  
High Frequency Vibrations ◽  
Surface Distress

Contacting surfaces can give rise to short pressure pulses (Smith shocks) when asperities interact and the resulting high-frequency vibrations, detected by accelerometers, can indicate surface distress to allow condition monitoring. Previous work had been limited by the test technique used so in this work vibration was recorded directly to computer memory to give a clearer idea of vibration patterns after failure of lubrication.

Continuous monitoring of physical parameters (temperature, electrical conductivity, water pressure) in a karst aquifer of central Italy (Venafro Mts., Molise): first results in a seismically active region

2020 ◽  
Author(s):  
Gaetano De Luca ◽  
Giuseppe Di Carlo ◽  
Alberto Frepoli ◽  
Marco Moro ◽  
Luca Pizzino ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
High Frequency ◽  
Continuous Monitoring ◽  
Water Pressure ◽  
Karst Aquifer ◽  
Central Italy ◽  
Physical Parameters ◽  
Hydraulic Pressure ◽  
Earthquake Cycle ◽  
Stress Changes

<p>The involvement of fluids in the earthquake cycle is a still open debate in the scientific community (e.g. Gratier et al., 2002). In the last years, new data from laboratory experiments and on-field discrete and continuous monitoring of soil gas, springs and gas vents were gathered worldwide (e.g. Martinelli, 2015; Nielsen et al., 2016). The aim of these studies was to better define the role of the observed fluid changes either as a trigger of earthquakes or as the co and post-seismic response to the transient (dynamic) and permanent (static) stress changes. This subject is particularly attractive in central and southern Apennines (Italy), where both huge water and CO<sub>2</sub> circulation at depth, occur (e.g Frondini et al., 2018). In this respect, the three long-lasting earthquake sequences that hit central Apennine in the last decades (1997, 2009 and 2016-2017, M<sub>w</sub> up to 6.5) were accompanied by hydrological (increase or decrease in the spring discharges) and hydrochemical (variations in chemical composition, physico-chemical parameters) anomalies (e.g. Carro et al., 2005; Barberio et al., 2017; Petitta et al., 2018). Changes were observed mainly in the co and post-seismic phase and only a few pre-seismic signals were recorded. Temporal monitoring ranged from weeks to months, but higher sampling rates are needed to study crustal deformation processes (stress and volumetric strain) during the earthquake cycle. For example, since 2015 De Luca et al. (2016, 2018) are been performing high frequency (up to 20 samples/second) continuous monitoring of temperature, hydraulic pressure, and electrical conductivity in the Gran Sasso aquifer. They recorded unambiguous long-term (days to months) pre-Amatrice earthquake anomalies in both hydraulic pressure and electrical conductivity, related to its preparation stage.</p><p>In the light of the above, we decided to duplicate the equipment presently working in the Gran Sasso aquifer in a site with similar hydrological setting: the Venafro carbonate hydrostructure (Molise, Saroli et al., 2019). The site we chose is located in one of the most seismically active sectors of central-southern Apenninic belt, repeatedly hit in the past by large magnitude earthquakes and crossed by up to 20 km-long extensional fault systems (e.g. Galli & Naso, 2009). The main goals of our research are: i) measuring and understanding the dynamics of the carbonate aquifer, also through the analysis of rainfall, ii) deepening the relationships between aquifer behavior and earthquakes as well as to iii) widen the monitored areas.</p><p>Our experimental equipment includes a 3-channels 24-bit ADC set up for continuous local recording in groundwater (De Luca et al., 2016, 2018) in a horizontal borehole located in the drainage gallery “San Bartolomeo”, managed by Campania Aqueduct company. We started data acquisition in May 2019 by high-frequency continuous sampling (20 Hz for each channel) of physical parameters such as groundwater hydraulic pressure, temperature and electrical conductivity. We present some preliminary results (elaborated through a statistical approach) and possible explanations regarding the hydraulic pressure signals recorded before and during nearby (Mw 4.4, distance ~ 45 km) and regional (Albania, Mw 6.2, distance ~ 400 km) earthquakes, both occurred in November 2019.</p>

The use of SHM to monitor and evaluate bridge movements – absolute and accumulated – at the structure’s bearings and expansion joints

2021 ◽  
Author(s):  
Niculin Meng ◽  
Thomas Richli ◽  
Colm O’Suilleabhain
Keyword(s):  
Health Monitoring ◽  
High Frequency ◽  
Continuous Monitoring ◽  
Early Stage ◽  
Cycle Performance ◽  
High Frequency Data ◽  
Frequency Data ◽  
Expansion Joints ◽  
Potential Problems ◽  
Over Time

<p>The movements a bridge experiences, both absolute and accumulated over time, can significantly influence the structure’s life-cycle performance – especially as it relates to the components that facilitate these movements. Structural health monitoring (SHM) systems, with sensors placed at – or ideally, integrated in – a bridge’s bearings and expansion joints, can be used to efficiently record and evaluate these movements, facilitating continuous monitoring of the components’ and the structure’s performance over time. This can enable potential problems to be recognised at an early stage, and maintenance (e.g. replacement of “wear parts” such as sliding materials) to be optimised. The significance of the frequency at which measurements are recorded must be appreciated, as high-frequency data can capture micro-movements (e.g. due to wind or traffic) that far exceed the slow thermal movements. This paper explores this topic with reference to a number of case studies.</p>

scholarly journals Quantitative Analysis of the Sensitivity of UHF Sensor Positions on a 420 kV Power Transformer Based on Electromagnetic Simulation

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 3 ◽  
Author(s):  
Chandra Prakash Beura ◽  
Michael Beltle ◽  
Stefan Tenbohlen ◽  
Martin Siegel
Keyword(s):  
Sensitivity Analysis ◽  
High Frequency ◽  
Continuous Monitoring ◽  
Power Transformer ◽  
Tank Wall ◽  
Realistic Situation ◽  
Three Phase ◽  
Signal Sensitivity ◽  
Sensitive Sensor ◽  
Sensor Positions

With an increasing interest in ultra-high frequency (UHF) partial discharge (PD) measurements for the continuous monitoring of power transformers, it is necessary to know where to place the UHF sensors on the tank wall. Placing a sensor in an area with many obstructions may lead to a decrease in sensitivity to the UHF signals. In this contribution, a previously validated simulation model of a three-phase 300 MVA, 420 kV power transformer is used to perform a sensitivity analysis to determine the most sensitive sensor positions on the tank wall when PD activity occurs inside the windings. A matrix of UHF sensors located on the transformer tank is used to perform the sensitivity analysis. Some of the windings are designed as layer windings, thus preventing the UHF signals from traveling through them and creating a realistic situation with very indirect propagation from source to sensor. Based on these findings, sensor configurations optimized for UHF signal sensitivity, which is also required for PD source localization, are recommended for localization purposes. Additionally, the propagation and attenuation of the UHF signals inside the windings and the tank are discussed in both oil and air.

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