A distributed sensing capability for in situ time-domain separation of Lamb waves

2013 ◽  
Author(s):  
N. Rajic ◽  
C. Rosalie ◽  
C. Davis ◽  
P. Norman
Keyword(s):  
Time Domain ◽  
Lamb Waves ◽  
Distributed Sensing ◽  
Domain Separation

Measuring transient solute transport through the vadoze zone using time domain reflectometry

Soil Research ◽  
2001 ◽  
Vol 39 (6) ◽  
pp. 1359 ◽  
Author(s):  
I. Vogeler ◽  
S. Green ◽  
A. Nadler ◽  
C. Duwig
Keyword(s):  
Electrical Conductivity ◽  
Solute Transport ◽  
Time Domain ◽  
Deterministic Model ◽  
Soil Surface ◽  
Time Domain Reflectometry ◽  
Richards Equation ◽  
Electrical Conductivities ◽  
Destructive Measurement

Time domain reflectometry (TDR) was used to monitor the transport of conservative tracers in the field under transient water flow in a controlled experiment under a kiwifruit vine. A mixed pulse of chloride and bromide was applied to the soil surface of a 16 m2 plot that had been isolated from the surrounding orchard soil. The movement of this solute pulse was monitored by TDR. A total of 63 TDR probes were installed into the plot for daily measurements of both the volumetric water content (θ) and the bulk soil electrical conductivity (σa). These TDR-measured σa were converted into pore water electrical conductivities (σw) and solute concentrations using various θ–σa–σw relationships that were established in the laboratory on repacked soil. The depth-wise field TDR measurements were compared with destructive measurement of the solute concentrations at the end of the experiment. These results were also compared with predictions using a deterministic model of water and solute transport based on Richards’ equation, and the convection–dispersion equation. TDR was found to give a good indication of the shape of the solute profile with depth, but the concentration of solute was under- or over-estimated by up to 50%, depending on the θ–σa–σw relationships used. Thus TDR can be used to monitor in situ transport of contaminants. However, only rough estimates of the electrical conductivity of the soil solution can so far be obtained by TDR.

An Innovative Use of TDR Probes: First Numerical Validations with a Coaxial Cable

2018 ◽  
Vol 23 (4) ◽  
pp. 437-442
Author(s):  
Raffaele Persico ◽  
Iman Farhat ◽  
Lourdes Farrugia ◽  
Sebastiano D'Amico ◽  
Charles Sammut
Keyword(s):  
Magnetic Properties ◽  
Transmission Line ◽  
Time Domain ◽  
Numerical Data ◽  
Time Domain Reflectometry ◽  
Coaxial Cable ◽  
Transmission Line Model ◽  
Properties Of Materials

In this paper we propose a study regarding some possibilities that can be offered by a time domain reflectometry (TDR) probe in retrieving both dielectric and magnetic properties of materials. This technique can be of interest for several applications, among which the characterization of soil in some situations. In particular, here we propose an extension of the paper “Retrieving electric and magnetic propetries of the soil in situ: New possibilities”, presented at the IWAGPR, held in Edinburgh in 2017, and as a new contribution we will validate a transmission line model with numerical data simulated by the CST code.

scholarly journals Multidisciplinary Characterization of Chlorinated Solvents Contamination and In-Situ Remediation with the Use of the Direct Current Resistivity and Time-Domain Induced Polarization Tomography

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 487 ◽  
Author(s):  
Aristeidis Nivorlis ◽  
Torleif Dahlin ◽  
Matteo Rossi ◽  
Nikolas Höglund ◽  
Charlotte Sparrenbom
Keyword(s):  
Direct Current ◽  
Time Domain ◽  
Chlorinated Solvents ◽  
Induced Polarization ◽  
Contaminated Sites ◽  
In Situ Remediation ◽  
Polarization Tomography ◽  
Refraction Tomography

Soil contamination is a widespread problem and action needs to be taken in order to prevent damage to the groundwater and the life around the contaminated sites. In Sweden, it is estimated that more than 80,000 sites are potentially contaminated, and therefore, there is a demand for investigations and further treatment of the soil. In this paper, we present the results from a methodology applied in a site contaminated with chlorinated solvents, for characterization of the contamination in order to plan the remediation and to follow-up the initial step of in-situ remediation in an efficient way. We utilized the results from three different methods; membrane interface probe for direct measurement of the contaminant concentrations; seismic refraction tomography for investigating the depth to the bedrock interface; and direct current resistivity and time-domain induced polarization tomography to acquire a high-resolution imaging of the electrical properties of the subsurface. The results indicate that our methodology is very promising in terms of site characterization, and furthermore, has great potential for real-time geophysical monitoring of contaminated sites in the future.

Thermo–time domain reflectometry method: Advances in monitoring in situ soil bulk density

2020 ◽  
Vol 84 (5) ◽  
pp. 1354-1360
Author(s):  
Yili Lu ◽  
Xiaona Liu ◽  
Meng Zhang ◽  
Joshua Heitman ◽  
Robert Horton ◽  
...  
Keyword(s):  
Bulk Density ◽  
Time Domain ◽  
Soil Bulk Density ◽  
Time Domain Reflectometry

Distributed Strain Sensing Using Carbon Nanotube Thin Films and Electrical Time-Domain Reflectometry

2018 ◽  
Author(s):  
Bo Mi Lee ◽  
Kenneth J. Loh ◽  
Francesco Lanza di Scalea
Keyword(s):  
Thin Films ◽  
Carbon Nanotube ◽  
Transmission Line ◽  
Time Domain ◽  
Structural Response ◽  
Time Domain Reflectometry ◽  
Distributed Sensing ◽  
Uniaxial Tensile ◽  
Electromagnetic Signal ◽  
Single Measurement

Nondestructive inspection (NDI) is an effective technique to inspect, test, or evaluate the integrity of materials, components, and structures without interrupting the serviceability of a system. Despite recent advances in NDI techniques, most of them are either limited to sensing structural response at their instrumented locations or require multiple sensors and measurements to localize damage. In this study, a new NDI system that could achieve distributed sensing using a single measurement was investigated. Here, piezoresistive carbon nanotube (CNT)-polymer thin film sensors connected in a transmission line setup were interrogated using electrical time-domain reflectometry (ETDR). In ETDR, an electromagnetic signal is sent from one end of the transmission line. When the signal encounters the sensor, it can partially reflect and be captured at the same point. The characteristics of the reflected signal depend on the sensor’s impedance, which is correlated to structural response, deformation, or damage. The advantage of this is that distributed sensing along the entire transmission line can be achieved using a single measurement point. To validate this concept, CNT-polymer thin films that were integrated with a transmission line are subjected to uniaxial tensile strains applied using a load frame. The ETDR signals were analyzed to assess the system’s sensing performance.

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