scholarly journals Theory and Guidelines for the Application of the Geophysical Sensor EM38

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4293 ◽  
Author(s):  
Heil ◽  
Schmidhalter
Keyword(s):  
Temperature Effects ◽  
Theoretical Background ◽  
Soil Variability ◽  
Soil Parameters ◽  
Depth Information ◽  
Soil Sensors ◽  
Geophysical Techniques ◽  
Apparent Electrical Conductivity ◽  
Agricultural Areas

Characterization of spatial soil variability is key for a better understanding of soils. To arrive at such information geophysical techniques have been used in the last two decades. Due to its easy handling, the geophysical sensor EM38 has widely been used to characterize agricultural areas. The theoretical background and usage of the EM38 is described, and based on multifaceted applications, the interpretation of the results as well as optimized steps for using it are outlined. Common principles and models of the apparent electrical conductivity (ECa) and strengths and limitations of this technique (calibration and temperature effects) are described as well as additional applications, such as the magnetic susceptibility, a comparison of measurements in vertical and horizontal modes, the use of weighted depth information and the influence of measurement conditions are addressed. Further a comparison of EM38 with other proximal soil sensors and fusion with other devices is described. The study reveals that EM38 is useful because the readings can reflect many different soil parameters.

Characterization of carbides in M50NiL

1991 ◽  
Vol 49 ◽  
pp. 606-607
Author(s):  
L. S. Lin ◽  
K. P. Gumz ◽  
A. V. Karg ◽  
C. C. Law
Keyword(s):  
Temperature Effects ◽  
Base Composition ◽  
Lattice Parameter ◽  
Control Surface ◽  
Carbide Formation ◽  
Particle Sizes ◽  
Low Carbon ◽  
Fee Structure ◽  
Heat Treated

Carbon and temperature effects on carbide formation in the carburized zone of M50NiL are of great importance because they can be used to control surface properties of bearings. A series of homogeneous alloys (with M50NiL as base composition) containing various levels of carbon in the range of 0.15% to 1.5% (in wt.%) and heat treated at temperatures between 650°C to 1100°C were selected for characterizations. Eleven samples were chosen for carbide characterization and chemical analysis and their identifications are listed in Table 1.Five different carbides consisting of M6C, M2C, M7C3 and M23C6 were found in all eleven samples examined as shown in Table 1. M6C carbides (with least carbon) were found to be the major carbide in low carbon alloys (<0.3% C) and their amounts decreased as the carbon content increased. In sample C (0.3% C), most particles (95%) encountered were M6C carbide with a particle sizes range between 0.05 to 0.25 um. The M6C carbide are enriched in both Mo and Fe and have a fee structure with lattice parameter a=1.105 nm (Figure 1).

Assessment of multiple geophysical techniques for the characterization of municipal waste deposit sites

2017 ◽  
Vol 145 ◽  
pp. 74-83 ◽  
Author(s):  
Gaël Dumont ◽  
Tanguy Robert ◽  
Nicolas Marck ◽  
Frédéric Nguyen
Keyword(s):  
Municipal Waste ◽  
Geophysical Techniques ◽  
Waste Deposit

Spatial prediction of soil parameters after wildfire and their relationship with ecological process of soil and vegetation

2021 ◽  
Author(s):  
David Banda Carrasco ◽  
Violeta Tolorza ◽  
Mauricio Galleguillos
Keyword(s):  
Prediction Interval ◽  
Additive Model ◽  
Chemical Characterization ◽  
Spatial Prediction ◽  
Ecosystem Dynamics ◽  
Burn Severity ◽  
Soil Parameters ◽  
Predictive Variables ◽  
Interval Coverage

&lt;p&gt;Novel estimations of burn severity consequences are relevant to improve the understanding of spatial ecosystem dynamics between soil and vegetation. In this study, we implemented digital soil mapping (DSM) with Random Forest (RF) and generalized additive model (GAM) as internal statistical models, to generate maps for spatial prediction of chemical parameters of post-fire litter (N, P, C and OM) in the Purapel River basin, Maule region of Chile. Response variables were the chemical characterization of 67 samples of litter collected in different hillslopes of the basin during the first post-fire winter. The predictive variables that fed the RF model were spectral, topographic, and vegetation structure derivations, obtained from free and private use satellite products (Sentinel 1, Sentinel 2, LiDAR and TanDEM-X). As a result, we generated maps of post-fire spatial distribution of N, P, C and OM with acceptable adjustment (R&lt;sup&gt;2&lt;/sup&gt; 0.52-0.61, nRMSE 54-72, pbias 0.35-1.20). The uncertainty associated with the predictions of these variables was successfully evaluated with the prediction interval coverage probability (PICP). A clear decrease on the concentration of litter elements is observed respect to the degree of burn severity, and this relationship depends on the type of cover and the environmental gradient where they are distributed.&lt;/p&gt;

Subsurface Investigation

2015 ◽  
pp. 744-795
Keyword(s):  
Field Tests ◽  
Field Investigation ◽  
Soil Parameters ◽  
Near Surface ◽  
Ground Investigation ◽  
Geophysical Techniques ◽  
Vertical Profiling ◽  
Sample Recovery ◽  
Subsurface Investigation ◽  
A Site

A good knowledge about a site including its subsurface conditions is very important in its safe and economical development. It is therefore an essential preliminary to the construction of any civil engineering work. This chapter outlines the objectives of site characterization and the general objectives of geotechnical investigation. It discusses the phases of field investigation and the stages of a full exploratory program including methods of sample recovery and field tests and sampling methods. Geophysical techniques can contribute very greatly to the process of ground investigation by allowing an assessment, in qualitative terms, of the lateral variability and vertical profiling of the near-surface materials beneath a site. Some of these geophysical techniques are discussed in the chapter. Laboratory examination/verification and testing should be made of representative portions of the samples to establish appropriate soil parameters. Some soil parameters may be estimated by correlations. The results of the subsurface investigation and related testing, together with interpretations, discussions, and foundation recommendations, are usually presented in the form of a detailed soil report.

scholarly journals Multiple Geophysical Techniques for Investigation and Monitoring of Sobradinho Landslide, Brazil

2019 ◽  
Vol 11 (23) ◽  
pp. 6672 ◽  
Author(s):  
Yawar Hussain ◽  
Martin Cardenas-Soto ◽  
Salvatore Martino ◽  
Cesar Moreira ◽  
Welitom Borges ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Geophysical Methods ◽  
Spectral Ratio ◽  
Dynamic Monitoring ◽  
Physical Parameters ◽  
Sliding Surface ◽  
Time Duration ◽  
Geophysical Techniques ◽  
Short Time

Geophysical methods have a varying degree of potential for detailed characterization of landslides and their dynamics. In this study, the application of four well-established seismic-based geophysical techniques, namely Ambient Noise Interferometry (ANI), Horizontal to Vertical Spectral Ratio (HVSR), Multi-Channel Analysis of Surface Waves (MASW) and Nanoseismic Monitoring (NM), were considered to examine their suitability for landslide characterization and monitoring the effect of seasonal variation on slope mass. Furthermore, other methods such as Ground Penetrating Radar (GPR) and DC Resistivity through Electrical Resistivity Tomography (ERT) were also used for comparison purpose. The advantages and limitations of these multiple techniques were exemplified by a case study conducted on Sobradinho landslide in Brazil. The study revealed that the geophysical characterization of the landslide using traditional techniques (i.e., GPR, ERT and MASW) were successful in (i) the differentiation between landslide debris and other Quaternary deposits, and (ii) the delineation of the landslide sliding surface. However, the innovative seismic based techniques, particularly ambient noise based (HVSR and ANI) and emitted seismic based (NM), were not very effective for the dynamic monitoring of landslide, which might be attributed to the short-time duration of the data acquisition campaigns. The HVSR was also unsuccessful in landslide site characterization i.e., identification of geometry and sliding surface. In particular, there was no clear evidence of the light seasonal variations, which could have been potentially detected from the physical parameters during the (short-time) ambient noise and microseismic acquisition campaigns. Nevertheless, the experienced integration of these geophysical techniques may provide a promising tool for future applications.

scholarly journals Load-Independent Characterization of Plate Foundation Support Using High-Resolution Distributed Fiber-Optic Sensing

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3518 ◽  
Author(s):  
Asmus Skar ◽  
Assaf Klar ◽  
Eyal Levenberg
Keyword(s):  
High Resolution ◽  
Mechanical Model ◽  
Fiber Optic ◽  
Soil Parameters ◽  
Soil Reaction ◽  
Model Parameters ◽  
Strain Sensing ◽  
Soil Response ◽  
Monitoring Strategies

The evaluation of soil reaction in geotechnical foundation systems such as concrete pavements, mat- and raft foundations is a challenging task, as the process involves both the selection of a representative mechanical model (e.g., Winkler, Continuum, Pasternak, etc.) and identify its prevailing parameters. Moreover, the support characteristics may change with time and environmental situation. This paper presents a new method for the characterization of plate foundation support using high-resolution fiber-optic distributed strain sensing. The approach involves tracking the location of distinct points of zero and maximum strains, and relating the shift in their location to the changes in soil reaction. The approach may allow the determination of the most suited mechanical model of soil representation as well as model parameters. Routine monitoring using this approach may help to asses the degradation of the subsoil with time as part of structural health monitoring strategies. In this paper, fundamental expressions that relate between the location of distinct strain points and the variation of soil parameters were developed based on various analytical foundation support models. Finally, as an initial validation step and to underpin the idea basics, the proposed method was successfully demonstrated on a simple mechanical setup. It is shown that the approach allows for load-independent characterization of the soil response and, in that sense, it is superior to common identification methods.

A survey of entomopathogenic nematodes and their symbiotic bacteria in agricultural areas of northern Thailand

2020 ◽  
Vol 94 ◽  
Author(s):  
J. Ardpairin ◽  
P. Muangpat ◽  
S. Sonpom ◽  
A. Dumidae ◽  
C. Subkrasae ◽  
...  
Keyword(s):  
Entomopathogenic Nematodes ◽  
Biocontrol Agent ◽  
Insect Pests ◽  
Soil Samples ◽  
Symbiotic Bacteria ◽  
Soil Parameters ◽  
Field Crops ◽  
Indian Strain ◽  
Agricultural Areas ◽  
28S Ribosomal Dna

Abstract Entomopathogenic nematodes (EPNs) Steinernema and Heterorhabditis and their symbiotic bacteria, Xenorhabdus and Photorhabdus, have been successfully used for the control of insect pests. The objectives of this study were to survey the EPNs and symbiotic bacteria in the agricultural areas of the Phitsanulok province, Thailand, and to study the association between the soil parameters and presence of EPNs. We collected 200 soil samples from 40 soil sites in agricultural areas (field crops, horticulture crops and forest). The prevalence of EPNs was 8.0% (16/200). Fifteen of the EPN isolates were molecularly identified (based on 28S ribosomal DNA and internal transcribed spacer regions) as Steinernema siamkayai. Seven isolates of Xenorhabdus stockiae were identified using recombinase A sequencing. Phylogenetic analysis revealed that all the Steinernema and Xenorhabdus isolates were closely related to S. siamkayai (Indian strain) and X. stockiae (Thai strain), respectively. Significantly more EPNs were recovered from loam than from clay. Although the association between soil parameters (pH, temperature and moisture) and the presence of EPNs was not statistically significant, the elevation levels of the soil sites with and without EPNs were found to be different. Moreover, statistical comparisons between the agricultural areas revealed no significant differences. Therefore, we concluded that S. siamkayai is associated with X. stockiae in agricultural areas and that there is no association between the soil parameters of agricultural areas and presence of EPNs, except for soil texture and the elevation. Steinernema siamkayai may be applied as a biocontrol agent in agricultural areas.

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