Automatic electrical resistance soil-moisture measuring system. Technical note

Author(s):  
T.H.L. Williams
2019 ◽  
pp. 128-138
Author(s):  
V. S. Yagubov ◽  
A. V. Shchegolkov ◽  
A. V. Shchegolkov ◽  
N. R. Memetov

Developing "smart" materials with improved both structural and functional characteristics is one of the promising areas of materials science. Measuring the electrical resistance of CNTs-modified (various mass contents) polymers and in particular, elastomers during performing several tests (compression, stretching, and torsion) at a constant current is relevant in electrical engineering, mechanical engineering, aviation, and space industry. Changes in the elastomer shape under different types of testing lead to the destruction of macromolecules and the structuring of the material as a whole. Therefore, it is important to study the effect of CNTsbased modifying fillers on the elastomer. When compressing, stretching or twisting the nano-modified elastomer, along with the mutual movement of its macromolecular fragments and aggregates, the modifier particles also move, which generally determines the transport of electrons in the resulting structure and affects the physical and mechanical parameters of the composite material. To conduct studies, elastomers containing different amounts of a CNTs-based modifying filler were prepared. To investigate and elucidate relevant dependencies, a measuring system (MS) was constructed, which makes it possible to determine electrical resistance values of the composite material with different CNTs contents in the polymer matrix composition exposed to various mechanical loads. Basing the research results, it was established that the electrical resistance of the elastomer composites modified with 1.0–2.5 wt.% CNTs decreases when compressing from 0 to 100 N, whereas when the compression force ranges from 100 to 350 N, the electrical resistance remains unchanged. When the elastomer composites modified with 2–2.5 wt.% CNTs were stretched by 30–40 %, the electrical resistance was found to increase from 5·103 to 1.9·107 Ω.


2010 ◽  
Vol 14 (2) ◽  
pp. 271-277 ◽  
Author(s):  
E. Peled ◽  
E. Dutra ◽  
P. Viterbo ◽  
A. Angert

Abstract. In the past years there have been many attempts to produce and improve global soil-moisture datasets and drought indices. However, comparing and validating these various datasets is not straightforward. Here, interannual variations in drought indices are compared to interannual changes in vegetation, as captured by NDVI. By comparing the correlations of the different indices with NDVI we evaluated which drought index describes most realistically the actual changes in vegetation. Strong correlation between NDVI and the drought indices were found in areas that are classified as warm temperate climate with hot or warm dry summers. In these areas we ranked the PDSI, PSDI-SC, SPI3, and NSM indices, based on the interannual correlation with NDVI, and found that NSM outperformed the rest. Using this best performing index, and the ICA (Independent Component Analysis) technique, we analyzed the response of vegetation to temperature and soil-moisture stresses over Europe.


1993 ◽  
Vol 3 (2) ◽  
pp. 195-197 ◽  
Author(s):  
Ben Faber ◽  
James Downer ◽  
Lori Yates

Soil moisture status can be measured using neutron probes, time domain reflectometry, tensiometers, gravimetric methods, and electrical resistance blocks. Most methods have limitations; they may be time-consuming (gravimetric), expensive (neutron probe, time domain), or fixed in place (tensiometer, gypsum block, and neutron probe) (Schmugge, 1980; Weems, 1991). Water management in droughty, urban areas of the country would benefit from identification of a portable, fast, and relatively inexpensive soil moisture measuring device suitable for use in urban lawns and gardens. In this study, we have identified an instrument that may be suitable for this purpose.


2020 ◽  
Vol 24 (3) ◽  
pp. 1073-1079
Author(s):  
Amirhossein Mazrooei ◽  
Arumugam Sankarasubramanian ◽  
Venkat Lakshmi

Abstract. Providing accurate soil moisture (SM) conditions is a critical step in model initialization in weather forecasting, agricultural planning, and water resources management. This study develops monthly-to-seasonal (M2S) top layer SM forecasts by forcing 1- to 3-month-ahead precipitation forecasts with Noah3.2 Land Surface Model. The SM forecasts are developed over the southeastern US (SEUS), and the SM forecasting skill is evaluated in comparison with the remotely sensed SM observations collected by the Soil Moisture Active Passive (SMAP) satellite. Our results indicate potential in developing real-time SM forecasts. The retrospective 18-month (April 2015–September 2016) comparison between SM forecasts and the SMAP observations shows statistically significant correlations of 0.62, 0.57, and 0.58 over 1-, 2-, and 3-month lead times respectively.


2005 ◽  
Vol 12 (1) ◽  
pp. 51-56 ◽  
Author(s):  
K. Bay ◽  
X. Zhou ◽  
W. Schneider ◽  
P. Brandstätt

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