Measuring soil bulk density profiles with a single probe gamma density gauge

Calibrating neutron depth gauges for measuring soil water content profiles requires soil bulk density data. In this study, the feasibility of using a single probe gamma density gauge to measure the soil wet bulk density was investigated for use in neutron gauge calibration. The same sites, access tubes, and conventional gravimetric soil data used for the ASCE Neutron Gauge Calibration Study were used for the Gamma Gauge Study. Iterative procedures were successfully developed to calibrate the gamma density gauge, and then to convert wet bulk density to dry bulk density data for the three soil sites studied

Effect of moisture and bulk density sampling on neutron moisture gauge calibration

Three moisture and bulk density sampling methods were evaluated for use in neutron gauge calibration. Each of the methods was comprised of a single core or portions of a core taken during installation of a neutron access tube. In addition to direct measurement of bulk density, the effect of using "smoothed", "probable" and gamma-probe measured bulk density profiles was evaluated. The use of these three alternative bulk density profiles in the computation of volumetric moisture generally had insignificant effect on the resulting neutron gauge calibration equation. The use of a depth-weighted volumetric moisture profile generally improved calibration statistics, but reduced slopes of neutron calibration equations (% moisture per count ratio). Overall, a total core method which used a tractor-mounted, hydraulically operated coring tool provided the most consistent calibrations with lowest standard errors of estimate, although compression of soil along the perimeter of the cored hole increased subsequent neutron count ratios. A "Madera" down-hole sampler generally provided good calibrations, also. A third, small-volume, down-hole sampler provided valid moisture and bulk density samples; however, the smaller representative volume of the sampler relative to the sampling volume of neutron gauges adversely affected slopes of some calibration equations

Neutron gauge calibration comparison of methods

Several methods for obtaining soil samples for determining soil water content were used for field calibration of neutron gauges. This paper compares the results of calibration curves obtained from the study data by comparing intercepts, slopes and correlation coefficients ("r" values). The study found differences in characteristics between gauges of the same brand, differences between brands and a great effect by access tube materials on the calibration curve

Soil bulk density sampling for neutron gauge calibration

The ASCE Task Committee on Neutron Gauge Calibration met in Logan, Utah in July 1992 to investigate the various methods of soil sampling, installation of access tubes, effect of various parameters on gauge readings, methods of developing field calibration curves and comparison of neutron gauge characteristics. Details of the overall objectives of the study are covered by Stone (1993, this volume). This paper discusses the soil sampling methods and presents a comparative result based on bulk density, time required for sampling and cost of sampling equipment Other papers developed from this study describe the soils, the three sites investigated and the problems related to the tube installation process

The ASCE neutron probe calibration study: overview

A workshop was held at Logan, Utah to gather field information on neutron probe calibration and operation. Several techniques and instruments were compared. This paper serves to establish the background information for the work and describe the overall approaches, conditions, and equipment. Other papers presented at this conference provide detailed procedures and results

Constraining the electric charges of some astronomical bodies in Reissner-Nordstrom spacetimes and generic r^-2-type power-law potentials from orbital motions

We put model-independent, dynamical constraints on the net electric charge Q of some astronomical and astrophysical objects by assuming that their exterior spacetimes are described by the Reissner-Nordstroem metric, which induces an additional potential U_RN \propto Q^2 r^-2. Our results extend to other hypothetical power-law interactions inducing extra-potentials U_pert = r^-2 as well (abridged).Comment: LaTex2e, 16 pages, 3 figures, no tables, 128 references. Version matching the one at press in General Relativity and Gravitation (GRG). arXiv admin note: substantial text overlap with arXiv:1112.351

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http://www.archive.org/details/constructionasse00dic

Effect of moisture and bulk density sampling on neutron moisture gauge calibration

Three moisture and bulk density sampling methods were evaluated for use in neutron gauge calibration. Each of the methods was comprised of a single core or portions of a core taken during installation of a neutron access tube. In addition to direct measurement of bulk density, the effect of using "smoothed", "probable" and gamma-probe measured bulk density profiles was evaluated. The use of these three alternative bulk density profiles in the computation of volumetric moisture generally had insignificant effect on the resulting neutron gauge calibration equation. The use of a depth-weighted volumetric moisture profile generally improved calibration statistics, but reduced slopes of neutron calibration equations (% moisture per count ratio). Overall, a total core method which used a tractor-mounted, hydraulically operated coring tool provided the most consistent calibrations with lowest standard errors of estimate, although compression of soil along the perimeter of the cored hole increased subsequent neutron count ratios. A "Madera" down-hole sampler generally provided good calibrations, also. A third, small-volume, down-hole sampler provided valid moisture and bulk density samples; however, the smaller representative volume of the sampler relative to the sampling volume of neutron gauges adversely affected slopes of some calibration equations

The ASCE neutron probe calibration study: overview

A workshop was held at Logan, Utah to gather field information on neutron probe calibration and operation. Several techniques and instruments were compared. This paper serves to establish the background information for the work and describe the overall approaches, conditions, and equipment. Other papers presented at this conference provide detailed procedures and results

Neutron gauge calibration comparison of methods

Several methods for obtaining soil samples for determining soil water content were used for field calibration of neutron gauges. This paper compares the results of calibration curves obtained from the study data by comparing intercepts, slopes and correlation coefficients ("r" values). The study found differences in characteristics between gauges of the same brand, differences between brands and a great effect by access tube materials on the calibration curve