Search results for "resistivity"
showing 10 items of 385 documents
Geophysical surveys for the restoration of Branciforte Palace in Palermo
2019
A multi-methodological and non-invasive geophysical study has been carried out in order to support the restoration project of the historic Branciforte Palace in Palermo. Ground Penetrating Radar profiles and an Electrical Resistivity Tomography ERT, carried out on the floor of the stable of the Palace, allowed to evaluate in detail the state of consolidation of the subsoil, in correspondence of a double row of marble columns, some of which were affected by differential subsidence. These columns have been investigated by means of Ultrasonic Tomography to verify their state of degradation. Moreover Infrared Thermography images of the internal and external walls and of the vaults highlighted d…
Impact of freezing rate on electrical conductivity of produce
2013
The aim of this work was to compare the effects of freezing rate on electrical conductivity of potatoes, carrots and apples. Electrical conductivity tests were conducted on a custom ohmic cell while samples texture was measured by means of a universal testing machine. The raw un-pretreated samples were used as control. This study showed that freezing pre-treatments lead to differences in electrical conductivity of considered samples, producing structural damage, the latter being relatively more severe when the tested products undergo ohmic treatment.
Investigation of diffusion and electromigration of hydrogen in palladium and PdAg alloy
1999
Abstract Diffusion and electromigration of hydrogen in PdH 0.1 , Pd 77 Ag 23 H 0.1 and Pd 50 Ag 50 H 0.1 alloy were measured by means of resistivity method. It is known that hydrogen migrates towards the cathode within the temperature range of 300–473 K in the PdH 0.1 and Pd 77 Ag 23 H 0.1 system. In Pd 50 Ag 50 H 0.1 , hydrogen migrates towards the cathode below 400 K, but towards the anode at higher temperatures. Its effective valency increases together with temperature. At the same time it satisfies the linear dependence on inverse specific resistance ρ : Z eff = Z i +( k / ρ ). The constants Z i and k have the following values: (1.05±0.01) and −(3.81±0.04)×10 −8 Ω m for hydrogen in PdH …
3D ERT for the study of an ancient wall covered by precious mosaics
2009
The DC electrical tomography (ERT) is still a method scarcely diffused for the study of masonry of recent and ancient buildings, in spite of the very high resolution power of this methodology. The major limitation on ERT applicability on precious surfaces (like masonries or floors with fresco or mosaic covering) depends on the method of current injection: usually it is necessary to drive electrodes (small nails) into small perforations on the surfaces, to obtain sufficiently high current values (to produce good signal to noise ratio). An interesting application of the MYG array (that reduces significantly, compared to other classical arrays, the number of electrodes utilized for current inj…
Variation in somatic cell count, California mastitis test, and electrical conductivity among various fractions of ewe's milk.
1991
Abstract Variation of three estimates of udder inflammation (SCC, California mastitis test, and electrical conductivity) among the foremilk, machine milk, and hand stripping samples were studied. Foremilk and hand stripping milks were taken from each individual teat; machine milk was taken from the entire udder. For this experiment a total of 30 Manchega ewes were subjected to machine milking during the 9th wk of lactation. Samples were taken in duplicate during two milkings on consecutive mornings. Significant differences were observed in the SCC and electrical conductivity, but not in California mastitis test, between foremilk and stripping milk The stripping fraction had higher SCC (70 ±…
Physico-chemical properties of dense water/copper(II) bis(2-ethylhexyl) sulfosuccinate/CCl4 microemulsions
2007
Measurements of some physico-chemical properties (density, viscosity, conductance, infra-red spectra) of water/copper(II) bis(2-ethylhexyl) sulfosuccinate (Cu(DEHSS)2)/CCl4 microemulsions, as a function of the volume fraction O of the dispersed phase (0 < O < 0.6) and of the molar ratio R (R = [water]/[DEHSS−]), have been performed at 25 °C. At each value of R, the density of the micellar phase is practically independent of O whereas the viscosity of microemulsions diverges above threshold O values. A divergent behavior for the electrical conductivity has also been observed but only at certain R values. These results, together with those from infra-red spectra, suggest that in percolated mi…
Electrical conductivity as a state indicator for the start-up period of anaerobic fixed-bed reactors.
2016
The aim of this work was to analyse the applicability of electrical conductivity sensors for on-line monitoring the start-up period of an anaerobic fixed-bed reactor. The evolution of bicarbonate concentration and methane production rate was analysed. Strong linear relationships between electrical conductivity and both bicarbonate concentration and methane production rate were observed. On-line estimations of the studied parameters were carried out in a new start-up period by applying simple linear regression models, which resulted in a good concordance between both observed and predicted values. Electrical conductivity sensors were therefore identified as an interesting method for monitori…
On the use of geophysical methods to characterize heterogeneities of quaternary alluvial deposits. Application to stormwater infiltration.
2007
Colloque avec actes et comité de lecture. International.; International audience; Stormwater infiltration basins are generally built on geological formations with large values of hydraulic conductivity. Such is the case for quaternary alluvial formations, among which are glaciofluvial deposits. Two geophysical investigation methods, namely ground-penetrating radar and electrical tomography, were tested on an infiltration basin built on a glaciofluvial deposit. Geophysical profiles were calibrated on a trench wall dug in the glaciofluvial formation. A sedimentological study coupled to geophysical measurements behind the trench wall highlights the three-dimensional architecture of the deposit…
Intégration d’une prospection géophysique dans la démarche de cartographie des sols : Exemple de l’unité expérimentale d’Epoisses
2016
Intégration d’une prospection géophysique dans la démarche de cartographie des sols : Exemple de l’unité expérimentale d’Epoisses. 13. Journées d'Etudes des Sols
Acoustic properties of plates with unevenly distributed macro perforations backed by woven meshes
2012
A hybrid model describing the acoustic properties of plates with macro-perforations that can be unevenly distributed on the plate surface and backed by woven or precision woven meshes with microscopic perforations is proposed. The plate perforations may be of circular or rectangular shapes. Since the perforated plate may not necessarily be considered as an equivalent fluid, its surface impedance is calculated by the Maa model [Noise Control Eng. J. 29, 77-84 (1987)], whereas the Johnson-Champoux-Allard model [J. Appl. Phys. 70, 1975-1979 (1991)] is used for the mesh. It is observed that the absorption of the carrying plate seems to depend on the hydraulic diameter of the perforations and no…