The effects of moisture, cation concentration, temperature, density and composition of soils on their electrical resistivity

The effects. of moisture, cation concentration, dens ity , temper~ t ure and grai n si ze on the electrical resistivity of so il s are examined using laboratory prepared soils. An i nexpen si ve method for preparing soils of different compositions was developed by mixing various size fractions i n the laboratory. Moisture and cation c oncentration are related to soil resistivity by powe r functions, whereas soil resistiv ity and temperature, density, Yo gravel, sand , sil t, and clay are related by exponential functions . A total of 1066 cases (8528 data) from all the experiments were used in a step-wise multiple linear r egression to determine the effect of each variable on soil resistivity. Six variables out of the eight variables studied account for 92.57/. of the total variance in so il resistivity with a correlation coefficient of 0.96. The other two variables (silt and gravel) did not increase the · variance. Moisture content was found to be - the most important Yo clay. variable- affecting s oil res istivi ty followed by These two variables account for 90.81Yo of the total variance in soil resistivity with a correlation ~oefficient ·.of 0 . 95. Based on these results an equation to ' ~~ed{ ct soil r esist ivi ty using moisture and Yo clay is developed . To t est the predicted equation, resistivity measurements were made on natural soils both in s i tu a nd i n the laboratory. The data show that field and laboratory measurements are comparable. The predicted regression line c losely coinciqes with resistivity data from area A and area B soils ~clayey and silty~clayey sands). Resistivity data and the predicted regression line in the case of c layey soils (clays> 40%) do not coincide, especially a t l ess than 15% moisture. The regression equation overestimates the resistivity of so i l s from area C and underestimates for area D soils. Laboratory prepared high clay soils give similar trends. The deviations are probably caused by heterogeneous distribution of mo i sture and difference in the type o f cl ays present in these soils.

The Effects of Annealing URu2Si2 on the Resistivity and Meissner Effect

The enigmatic heavy fermion URu2Si2, which is the subject of this thesis, has attracted intensive theoretical and experimental research since 1984 when it was firstly reported by Schlabitz et al. at a conference [1]. The previous bulk property measurements clearly showed that one second order phase transition occurs at the Hidden Order temperature THO ≈ 17.5 K and another second order phase transition, the superconducting transition, occurs at Tc ≈ 1 K. Though twenty eight years have passed, the mechanisms behind these two phase transitions are still not clear to researchers. Perfect crystals do not exist. Different kinds of crystal defects can have considerable effects on the crystalline properties. Some of these defects can be eliminated, and hence the crystalline quality improved, by annealing. Previous publications showed that some bulk properties of URu2Si2 exhibited significant differences between as-grown samples and annealed samples. The present study shows that the annealing of URu2Si2 has some considerable effects on the resistivity and the DC magnetization. The effects of annealing on the resistivity are characterized by examining how the Residual Resistivity Ratio (RRR), the fitting parameters to an expression for the temperature dependence of the resistivity, the temperatures of the local maximum and local minimum of the resistivity at the Hidden Order phase transition and the Hidden Order Transition Width ∆THO change after annealing. The plots of one key fitting parameter, the onset temperature of the Hidden Order transition and ∆THO vs RRR are compared with those of Matsuda et al. [2]. Different media used to mount samples have some impact on how effectively the samples are cooled because the media have different thermal conductivity. The DC magnetization around the superconducting transition is presented for one unannealed sample under fields of 25 Oe and 50 Oe and one annealed sample under fields of 0 Oe and 25 Oe. The DC field dependent magnetization of the annealed Sample1-1 shows a typical field dependence of a Type-II superconductor. The lower critical field Hc1 is relatively high, which may be due to flux pinning by the crystal defects.

Design of Resistivity Instrumentation for a He3 Cryostat and its Application to the Charge Density Wave Superconductor CuxTiSe2

Fermi patches in quasi-two dimensional charge density waves (CDW) have not described the connection to superconductivity (SC) according to theory adequately at this point in time. The connection between CDW and SC in the quasi-two dimensional material CuxTiSe2 is an interesting one which might reveal mechanisms in unconventional superconductors. A previous Brock graduate student grew crystals of CuxTiSe2. The precise doping of the samples was not known. In order to determine the doping parameter x in CuxTiSe2, a sensitive resistivity measurement system was necessary. A new resistivity measurement system was designed and implemented utilizing an Infrared Labs HDL-10 He3 cryostat. By comparing with data from the literature, doping of two samples was investigated using the new measurement system and a Quantum Design Magnetic Property Measurement System (MPMS). Methods for determining the doping revealed that the old resistivity system would not be able to determine the CDW transition temperature of highly doped samples or doping for elongated samples due to electronic noise. Doping in one sample was found to be between x=0.06 and x=0.065. Values of doping in the second sample had a discrepancy but could be explained by incorrect sample orientation.

Ribbed moraines and subglacial geomorphological signatures of interior-sector palaeo-ice sheet dynamics

Transverse, subglacial bedforms (ribbed moraines) occur frequently in southern Keewatin, Nunavut, Canada, where they record a complex glacial history, including shifting centers of ice dispersal and fluctuating basal thermal regimes. Comprehensive mapping and quantitative morphometric analysis of the subglacial bedform archive in this sector reveals that ribbed moraines are spatially clustered by size and assume a broad range of visually distinct forms. Results suggest that end-member morphologies are consistent with a dichotomous polygenetic origin, and that a continuum of forms emerged through subsequent reshaping processes of variable intensity and duration. Translocation of mobile, immobile and quasi-mobile beds throughout the last glacial cycle conditioned the development of a subglacial deforming bed mosaic, and is likely responsible for the patchy zonation of palimpsest and inherited landscape signatures within this former core region of the Laurentide Ice Sheet. Comparison against field evidence collected from central Norway suggests that bedforming processes can be locally mediated by pre-existing topography.

Handwritten sheet of paper detailing the cost of transporting boxes containing the Gravatt’s level

Handwritten sheet of paper detailing the cost of transporting boxes containing the Gravatt’s level from London to St. Catharines, April 1847.

Handwritten sheet of paper detailing the cost of transporting boxes containing the Gravatt’s level

Handwritten sheet of paper detailing the cost of transporting boxes containing the Gravatt’s level from London to St. Catharines. This sheet is signed by S.D. Woodruff, Jan. 11, 1847.

Pay roll voucher from the Engineer Department of Port Dalhousie and Thorold Railway Extension for repairs to fences and cattle guards etc. in the months of April and May. This document is attached to a time sheet, May 11, 1857

Pay roll voucher from the Engineer Department of Port Dalhousie and Thorold Railway Extension for repairs to fences and cattle guards etc. in the months of April and May. This document is attached to a time sheet, May 11, 1857.

Annual meeting of the Long Point Company attached to a copy of the May 31, 1882 balance sheet

Annual meeting of the Long Point Company (1 page, printed) attached to a copy of the May 31, 1882 balance sheet (1 page, printed). The meeting has the name J.I. Mackenzie, assistant secretary-treasurer on the bottom and the balance sheet has the names J.I. Mackenzie, secretary treasurer and Geo. H. Gillespie, auditor on the bottom of the page, June 6, 1882.

Balance sheet for 14 months ending May 31, 1879

Balance sheet (1 page, printed) for 14 months ending May 31, 1879.

Balance sheet including copy of the cash book and auditor’s report for 12 months ending May 31, 1880

Balance sheet including copy of the cash book and auditor’s report (1 page, printed) for 12 months ending May 31, 1880.

Balance sheet including copy of the cash book and auditor’s report for 12 months ending May 31, 1881

Balance sheet including copy of the cash book and auditor’s report (1 page, printed) for 12 months ending May 31, 1881.

Rough copy of the balance sheet to May 31, 1882

Rough copy of the balance sheet (3 pages, handwritten) to May 31, 1882.

Balance sheet including copy of the cash book and auditor’s report for 12 months ending May 31, 1882

Balance sheet including copy of the cash book and auditor’s report (1 page, printed) for 12 months ending May 31, 1882.

Receipt from W. H. Eckhardt, Pianos, Organs, Sheet Music and Musical Merchandise for piano

Receipt from W. H. Eckhardt, Pianos, Organs, Sheet Music and Musical Merchandise for piano, May 9, 1887.

Nanocompósitos bifuncionales magnético-luminiscentes de óxido de hierro en un polímero semiconductor.

Tesis (Maestría en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) UANL, 2010.