Electrical Resistivity Studies Research Articles

Experimental and numerical simulation studies of electrical resistance of cementitious materials under varying temperature history

Many in-service concrete structures are normally exposed to varying temperature condition. The time-dependent and non-uniform temperature distribution in concrete structures could affect the accurate assessment of their electrical properties. Therefore, the influences of temperature change over time and the spatial variation in temperature on the measured electrical resistance of cementitious materials are still in need of investigation. The coupled thermal-electrical responses of two types of cementitious materials under varying temperature history were investigated by a series of thermal and electrical tests in this study. Then a coupled thermal-electrical finite element (FE) model was developed to simulate the coupled thermal-electrical responses. The results show that the input direct current has a minor effect on the measured electrical resistance by embedded four-probe method and the specimen temperature when it is no greater than 3 mA. The relationship between the measured temperature at 10-mm depth of the specimen and the apparent resistance is well captured by a linear equation. The coupled thermal-electrical finite element model can predict well the developments of specimen temperature and apparent electrical resistance under varying temperature history. The FE results reveal that the non-uniform temperature variation results in the redistribution of electrical current within the tested specimen. However, electrical field between the two inner electrodes is always uniform when the embedded four-probe method is used, which is not affected by the non-uniform temperature variation.

Evaluating the durability performance of concrete containing clastic sand and GGBS

The manufacturing process of materials utilized in concrete production has environmental implications. The production of cement releases significant amounts of greenhouse gases, while the extraction of aggregates and sand poses challenges to the natural environment. To minimize the aforementioned challenges researchers are suggested to utilize industrial by-products as a partial alternative for these materials Fly ash, stone dust, GGBS, silica fume, and metakaolin are widely utilized alternatives to construction materials. The specific use of clastic sand as a partial substitute for fine aggregate has recently gained popularity . However, studies on the characteristics of concrete prepared using cementitious materials and clastic sand are very few. In this work, the effect of clastic sand with ground granulated blast furnace slag concrete is being investigated. The GGBS is added in place of cement from 0% to 45%. Further, clastic sand is added in different proportions in GGBS concrete. The electrical resistivity, water absorption, acid attack, and micro-structural studies are carried out on all mixes to know the durability properties. The results confirm that the addition of GGBS as a cementitious material enhances durability. The inclusion of 35% of GGBS as a substitute for cement is optimum for enhancing durability. Further, the inclusion of 35% GGBS as a cement substitute and 20% clastic sand shows a dense matrix and optimum results in enhancing durability. This is due to the pozzolanic activity of GGBS and clastic sand works as filler materials. This investigation suggests utilizing clastic sand along with GGBS as a cementitious material.

Studies of electrical resistivity and magnetic properties of CuFe and CuNiFe films prepared by magnetron sputtering

The Cu-Fe binary alloys exhibit severe elemental segregation, resulting in an inhomogeneous microstructure, which leads to differences in microregion magnetic properties, thus affecting their application. Employing magnetron sputtering to produce films is advantageous for achieving a consistent dispersion of Fe within the Cu matrix. Furthermore, the addition of Ni will result in a more uniform distribution of Fe and facilitate the formation of the ferromagnetic Ni3Fe phase. In this study, Cu100−xFex and Cu100−x(Ni3/4Fe1/4)x series films were prepared by magnetron sputtering technique. The magnetic properties of films are closely related to their ferromagnetic element content. An increase in the content of ferromagnetic elements leads to an improvement in the saturation magnetization (MS) strength and a decrease in the coercivity (HC). The formation of Fe-Fe pairs is more favorable for magnetic properties compared to Ni-Fe pairs. Meanwhile, by comparing with bulk alloys, the distribution of the magnetic elements severely affects the magnetic properties. Moreover, the resistivity of Cu100−xFex films (20.3–96.7 μΩ cm) is much higher than that of Cu100−x(Ni3/4Fe1/4)x films (15.6–60.6 μΩ cm), which depends on the magnetic properties. This study systematically analyzes the effect of the content and distribution of magnetic elements on magnetic and electrical properties.

Substantiation of optimal characteristics of the device for electroodontodiagnostics based on the study of complex electrical resistance of tooth tissues

AIM. Aim of this work is to substantiate the optimal characteristics of the apparatus for electroodontodiagnostics on the basis of studying the complex electrical resistance of tooth tissues.MATERIALS AND METHODS. The study of complex tissue resistance during electroodontodiagnostics in 50 patients aged from 18 to 55 years was carried out. A total of 181 teeth were studied. All the teeth studied were with formed roots. 52 teeth were intact, 40 teeth had been previously treated for caries, 26 teeth had carious process, 21 teeth were diagnosed with pulpitis, 9 teeth were diagnosed with periodontitis, 33 teeth had been previously subjected to endodontic treatment.RESULTS. The results of studying the complex tissue impedance during electroodontodiagnostics showed that the impedance module can be in a wide range from 120 kOhm to 3500 kOhm. At that, the main contribution to the complex impedance is made by the state of hard tissues of teeth.CONCLUSION. The obtained results showed that the device for electroodontodiagnostics should automatically in a continuous mode to measure impedance and according to it to control the supply of the necessary exponentially increasing alternating sinusoidal current with a frequency of 50 Hz.

Thermoelectric and photovoltaic properties of 12-BaBi2S4

In this report, we have investigated the structure and properties of the 12-BaBi2S4. A single crystal X-ray diffraction study shows that the 12-BaBi2S4 crystallizes in the hexagonal crystal system (space group = P63/m) with refined lattice parameters of a = b = 25.2687(10) Å, c = 4.1859(2) Å, and formula unit = Z = 12 at room temperature. The structure contains fifteen crystallographic independent sites, including three Ba, four Bi, and eight types of S atoms. A phase pure polycrystalline sample of 12-BaBi2S4 was synthesized by heating stoichiometric amounts of BaCO3 and Bi2O3 under a CS2 atmosphere. The phase pure sample is found to be a semiconductor with a direct bandgap of 1.3(1) eV. The polycrystalline 12-BaBi2S4 exhibits ultra-low thermal conductivity values, varying from 0.47 Wm−1K−1 at 323 K to 0.43 Wm−1K−1 at 773 K. The sample shows high values of the Seebeck coefficient (S = −300 μV/K to −210 μV/K) in the 323 K–773 K range with poor electrical conductivity values. The negative sign of the S implies that the sample is a n-type semiconductor. DFT studies of the 12-BaBi2S4 also predict semiconducting properties. We have explored the 12-BaBi2S4 sample for photovoltaic (PV) applications by fabricating a liquid junction solar cell, TiO2/CdS/12-BaBi2S4/Sn2−/S2−/MWCNTs@Ni, which delivered an efficiency enhanced by ∼12 % to the control cell based on sole CdS as the photo-sensitizer. Theoretical electronic structure calculations suggest the semiconducting nature of the 12-BaBi2S4 in agreement with the optical absorption and electrical resistivity studies.

Effect of rare earth (Sm3+) substitution in mixed Ni-Zn-Co ferrites: Structural, magnetic, and DC electrical resistivity studies

NiZnCo ferrite has good magnetic properties and is one of the core materials used in magnetic devices. The solid-state reaction approach is utilized to synthesize Ni0.4Zn0.35Co0.25Fe2-xSmxO4 (x = 0.0, 0.02, 0.04, 0.06, 0.08, and 0.1) ferrites for investigation of structural, morphological, functional, magnetic and electrical resistivity properties using various characterization techniques. The techniques used for characterization were XRD, SEM, FTIR, VSM, and DC electrical resistivity. XRD spectra were used to determine phase confirmation, cubic crystallite size, andtheir variation with dopant content. No additional phase or impurity was found. The SEM pictures revealed ahomogeneous spherical particle formation with minimal porosity. With absorption bands under 1000 cm−1, FTIR spectra indicate the formation of a spinel structure. Tetrahedral (580 to 599 cm−1) and octahedral (388 to 399 cm−1) bond changes can be seen in infrared spectra. The magnetic hysteresis curves revealed soft ferromagnetic behavior, with coercivity (Oe) (532.13 to 312.10Oe) rising and saturation magnetization (Ms) (83.51 to 60.75 emu/g) falling as doping concentration increased. The DC electrical resistivity of synthesized nanoparticles with various compositions was measured against higher temperatures to confirm their semiconductor nature. The findings demonstrated the typical decreasing trend with rising temperature.

An orthosteric/allosteric bivalent peptide agonist comprising covalently linked protease-activated receptor-derived peptides mimics in vitro and in vivo activities of activated protein C

BackgroundActivated protein C (APC) has anticoagulant and cytoprotective cell-signaling activities, which often require protease-activated receptor (PAR) 1 and PAR3 and PAR cleavages at noncanonical sites (R46-N47 and R41-G42, respectively). Some PAR1-derived (P1) peptides and PAR3-derived (P3) peptides, eg, P1-47-66 and P3-42-65, mimic APC’s cell signaling. In anti-inflammatory assays, these 2 peptides at low concentrations synergistically attenuate cellular inflammation. ObjectivesTo determine whether a P1 peptide covalently linked to a P3 peptide mimics APC’s anti-inflammatory and endothelial barrier stabilization activities. MethodsAnti-inflammatory assays employed stimulated THP-1 cells and caspase-1 measurements. Cultured human EA.hy926 or murine aortic endothelial cells (ECs) exposed to thrombin were monitored for transendothelial electrical resistance. Bivalent covalently linked P1:P3 peptides were studied for APC-like activities. ResultsIn anti-inflammatory assays, P1-47-55 was as active as P1-47-66 and some P3 peptides (eg, P3-44-54 and P3-51-65) were as active as P3-42-65. The bivalent P1:P3 peptide comprising P1-47-55-(Gly[10 residues])-P3-51-65 (designated “G10 peptide”) was more potently anti-inflammatory than the P1 or P3 peptide alone. In transendothelial electrical resistance studies of thrombin-challenged ECs, P1-47-55 and the G10 peptide mimicked APC’s protective actions. In dose-response studies, the G10 peptide was more potent than the P1-47-55 peptide. In murine EC studies, the murine PAR-sequence–derived G10 peptide mimicked murine APC’s activity. Anti-PAR1 and anti-PAR3 antibodies, but not anti–endothelial protein C receptor antibodies, abated G10’s cytoprotection, showing that G10’s actions involve PAR1:PAR3. G10 significantly increased survival in murine endotoxemia. ConclusionThe PAR-sequence–derived G10 peptide is a bivalent agonist that mimics APC’s cytoprotective, anti-inflammatory, and endothelial barrier–stabilizing actions and APC’s protection against endotoxemic mortality.

Combined transport and dielectric models and experimental characterization based on impedance spectroscopy for studying the microstructural and transport properties of electro-ceramic perovskites

Collective investigations on the electrical resistivity, complex dielectric permittivity, complex impedance, conductivity, and electric modulus properties of La0.55Ca0.45Mn0.8Nb0.2O3 (LCMNO) are conducted. The impedance spectroscopy (IS) technique is reviewed to examine the electrical and dielectric responses of the material according to the carrier displacement, including core-shell structure, grain boundary effects, dielectric relaxation (local relaxation), and long-range conduction (non-local relaxation). This technique can correlate the electrical and dielectric responses with the ceramics’ microstructural effects (grain boundary and grain (core-shell) zones). For LCMNO, the electrical resistivity study confirms the presence of a metal-semiconductor transition at TM-SC=66 K. It points towards a gradual crossover from the thermally activated Small Polaron Hopping (SPH) to the Variable Range Hopping (VRH) process at low temperatures and for T> TM-SC. The dielectric results confirm the presence of various types of polarization effects. The occurrence of a dipolar reorientation is attributed to long-range electrical conduction. In addition, the accumulation of the activated charge carriers increases the Maxwell-Wagner polarization resulting from an internal barrier layer capacitor (IBLC) microstructure. The electric modulus study confirms the existence of a correlation between the mobile charge carrier’s motions. From the complex impedance, dielectric, and electric modulus, it is possible to label a material’s conductive and dielectric natures (non-Debye-relaxation-type).

Applying Geophysical and Hydrogeochemical Methods to Evaluate Groundwater Potential and Quality in Middle Egypt

The El-Minia district is a location of interest for future urban development. Using hydrochemistry and electrical resistivity studies, this work aimed to evaluate the groundwater potentiality and it’s suitable for various uses. The groundwater potential in the study area was evaluated based on 24 VESs (vertical electrical soundings), and its quality was determined based on the analyses of 57 groundwater samples. EC (salinity index), Na% (salt hazard), SAR (ratio of sodium adsorption), chloride risks, SSP (soluble sodium percentage), MH (magnesium hazard), and other indicators were used to determine whether the collected water samples were suitable for irrigation. Four layers in the study area are mentioned in the geoelectrical cross-sections that have been constructed. The first is made up of silt and clay from the Nile River, while the second is made up of sandy clay, which has a resistivity range of 15 to 32 Ohm.m and a range thickness of 2 to 68 m. Dry limestone makes up the third layer; its resistivity ranges from 1222 to 3000 Ohm.m and its thickness varies between 75 and 95 m. The Eocene aquifer in the research area is represented by the final layer, which has a thickness of more than 250 m and resistivity values that range from 602 to 860 Ohm.m. Most groundwater samples that were collected are safe for drinking; however, none of them are fit for home usage because of their extreme hardness. According to the SAR and US diagram, RSC, KR, and PI, most groundwater samples from the Pleistocene and Eocene aquifers are fit for irrigation.

Effect of Sodium Citrate as Complexing Agent on the Electrodeposited CuZn Alloys: Electrochemical, Morphology, Structure, and Electrical Resistivity Studies

Effect of Sodium Citrate as Complexing Agent on the Electrodeposited CuZn Alloys: Electrochemical, Morphology, Structure, and Electrical Resistivity Studies

Effects of V concentration on the physical properties of Cr1−x Al x alloy system

Electrical resistivity (ρ), magnetic susceptibility (χ) and thermoelectric power (S) studies reported previously on the (Cr1-x Al x )99V1 alloy system indicate a suppression of antiferromagnetism in the concentration range 0.015 ≤ x ≤ 0.040. The present study incorporates Sommerfeld electronic specific heat coefficient (γ), thermal conductivity (κ), Hall coefficient (R H) and analyses of the previous results in order to have a comprehensive study of the alloy system. γ(x) depicts two peaks close to the same concentrations where dS/dT|T→2K(x) have minima, i.e. at x c1 ≈ 0.015 and x c2 ≈ 0.040. Such peaks and minima, respectively, have been considered as key signatures of quantum criticality (QC) in alloys of Cr. Evidence of band structure modification in the alloy system is shown by a change of slope in the Nordheim-Gorter (N-G) relationship showing a minimum at an extrapolated concentration x = 0.035. The slope is positive for the incommensurate (I) spin-density-wave (SDW) alloys with x < 0.035 and a negative for the commensurate (C) SDW alloys with x > 0.035. A behaviour reminiscent of changes in the band structure is also observed in the Lorenz number, L(x), for the alloy with x = 0. R H(T) results in the range 0 ≤ x ≤ 0.026 have a sharp increase in the charge carrier density, n 2K = [qR H(2k)]−1, at the ISDW to paramagnetic (P) phase transition. The concentrations x = 0.015 and x = 0.040 are therefore considered ISDW to P and P to CSDW quantum critical points, respectively.

Unusually strong electronic correlation and field-induced ordered phase in YbCo2

We report the first study of electrical resistivity, magnetization, and specific heat on YbCo2. The measurements on a single-phased sample of YbCo2 bring no evidence of magnetic ordering down to 0.3 K in a zero magnetic field. The manifestations of low Kondo temperature are observed. The specific heat value divided by temperature, C/T, keeps increasing logarithmically beyond 7 J/mol K2 with decreasing temperature down to 0.3 K without no sign of magnetic ordering, suggesting a very large electronic specific heat. Analysis of the magnetic specific heat indicates that the large portion of the low-temperature specific heat is not explained simply by the low Kondo temperature but is due to the strong intersite magnetic correlation in both the 3d and 4f electrons. Temperature-dependent measurements under static magnetic fields up to 7 T are carried out, which show the evolution of field-induced transition above 2 T. The transition temperature increases with increasing field, pointing to a ferromagnetic character. The extrapolation of the transition temperature to zero field suggests that YbCo2 is in the very proximity of the quantum critical point. These results indicate that in the unique case of YbCo2, the itinerant electron magnetism of Co 3d-electrons and the Kondo effect within the vicinity of quantum criticality of Yb 4f-local moments can both play a role.

Influence of Bi3+ substitution on the structural and magnetic properties of Pr0.6Sr0.4MnO3 ceramics

We report the structural and magnetic phase transition induced in Pr0.6Sr0.4MnO3 as Pr3+ ions are replaced by Bi3+. Analysis of Rietveld refinement of the X-ray diffraction data reveals a change in crystal symmetry from orthorhombic, space group Pnma for x ≤ 0.20 to Imma for x > 0.50. Across intermediate Bi3+ substitution (0.25 ≤ x ≤ 0.40), a structural phase coexistence of Pnma and Imma symmetry is found. Based on the combined studies of electrical and magnetic properties, a magnetic phase diagram for Bi substituted Pr0.6Sr0.4MnO3 samples is proposed here. The electrical resistivity and magnetization studies for partial Bi3+ substituted samples x ≤ 0.10 indicate samples to be ferromagnetic metallic with TC = 310 K and 290 K for x = 0.0 and 0.10 respectively. As Bi3+ concentration increases, TC decreases, and the system transforms to be antiferromagnetic insulating with TN = 158 K for x = 0.60 accompanied by a spin glass like state below 10 K. For samples with intermediate Bi3+ concentrations i.e., 0.25 ≤ x ≤ 0.40, field induced metamagnetic magnetization loops (M vs. H) imply the competitive coexistence of ferromagnetic and antiferromagnetic interactions in the same matrix. Also, the open loops in field dependent resistance curves (MR vs. H) for 0.20 ≤ x ≤ 0.40, specify the field induced transition from insulating to metallic state. The magnetoresistance improves on increasing Bi3+, with MR% reaching a maximum of 100% for 0.20 ≤ x ≤ 0.30 samples.

The Study of Electrical Resistance of Silver Nanowires in Isopropanol for Heater Application

Silver nanowire is one of the most attractive materials for making devices. In this work, we are interested in using silver nanowires for heater application. To get a good heater, the electrical resistance of the device should be low in order to generate a high temperature. The media to disperse nanowires is also important and helps inter-connection between nanowires. Hence, we study the different amounts of isopropanol (IPA) in water as the media to disperse silver nanowires. The nanowire solutions were prepared under different percentages of isopropanol varying from 0% to 100%. Optical images showed the dispersity of nanowires after the media evaporated. The electrical resistances of spun silver nanowires on glass slides were conducted. The results show that the electrical resistance of nanowires in different amounts of IPA was separated into 2 groups. First, from 0% to 50% of IPA, the electrical resistances were lower than 15 Ohms. Second, for 75% to 100% of IPA, the electrical resistances show more than 85 Ohms. After heater testing of the first group, the temperature is stable and repeatable with a certain applied voltage and current.

Theoretical and experimental studies of the electrical properties of electrical contact gasket for the graphitizing of electrode preparations in direct heating furnaces

The article presents the results of theoretical and experimental studies of specific contact electrical resistance (SCER) and specific electrical resistance (SER) of electrical contact gaskets (ECG) made of thermally expanded graphite (TEG) and intended for their placement on the ends of electrode blanks before their graphitization in direct heating furnaces – furnaces Castner's. The obtained data of SCER “graphite–gasket–graphite” and SER (or electrical conductivity) of the ECG material are needed to minimize the energy consumption of the graphitization process using numerical modeling of the thermoelectric state of Castner's furnaces in order to develop energy-efficient regulations for their operation.&#x0D; The method of two samples was used for the experimental determination of the SCER, and the theoretical-experimental approach was used for the study of the SER, which makes it possible to exclude the influence of the contact resistance between the experimental sample and the electrodes for supplying the electric current on the value of the measured quantity and is based on the solution of the inverse coefficient problem of electrical conductivity (ICPE) using experimental data obtained during the SCER study. &#x0D; A mathematical formulation of the ICPE was formulated, a numerical method and an algorithm for its solution were developed, and a study of the SER of the TEG at different values of temperature and pressure was carried out.&#x0D; Determination of SCER and SER was carried out for ECG material with an initial density of 1000 kg/m3 in the temperature range up to 250 °С under different pressures in the range of up to 1.75 MPa. The results of these studies are presented in the form of two-parameter dependences on pressure and temperature with extrapolation up to 3000 °C. The measurement error of SCER and SER by the specified methods is estimated to be within 4–5% in the intervals of temperature change up to 250 °С and pressure up to 1.75 MPa.&#x0D; The obtained SCER and SER dependences for the ECG material are needed to perform a numerical analysis of the thermoelectric state of Castner's furnaces in order to develop rational graphitization regulations.

(Magneto)Transport Properties of (TiZrNbNi)1−xCux and (TiZrNbCu)1−xCox Complex Amorphous Alloys

We present a systematic study of electrical resistivity, superconductive transitions and the Hall effect for three systems of compositionally complex amorphous alloys of early (TE) and late (TL) transition metals: (TiZrNbNi)1-xCux and (TiZrNbCu)1-xCox in a broad composition range of 0<x<0.5 as well as Ti0.30Zr0.15Nb0.15Cu0.2Ni0.2, Ti0.15Zr0.30Nb0.15Cu0.2Ni0.2 and Ti0.15Zr0.15Nb0.30Cu0.2Ni0.2. All samples showed high resistivity at room temperature, 140-240 μΩ cm, and the superconducting transition temperatures decreased with increasing late transition metal content, similar to binary amorphous and crystalline high-entropy TE-TL alloys. The Hall coefficient RH was temperature-independent and positive for all samples (except for (TiZrNbCu)0.57Co0.43), in good agreement with binary TE-TL alloys. Finally, for the temperature dependence of resistivity, as far as the authors are aware, we present a new model with two conduction channels, one of them being variable range hopping, such as the parallel conduction mode in the temperature range 20-200 K, with the exponent p=1/2. We examine this in the context of variable range hopping in granular metals.

A Review of Subsurface Electrical Conductivity Anomalies in Magnetotelluric Imaging.

After 70 years of development, magnetotelluric (MT), a remote sensing technique for subsurface electrical resistivity imaging, has been widely applied in resource exploration and the deep tectonic evolution of the Earth. The electrical resistivity anomalies and their quantitative interpretation are closely related to or even controlled by the interconnected high-conductivity phases, which are frequently associated with tectonic activity. Based on representative electrical resistivity studies mainly of the deep crust and mantle, we reviewed principal electrical conduction mechanisms, generally used conductivity mixing models, and potential causes of high-conductivity including the saline fluid, partial melting, graphite, sulfide, and hydrogen in nominally anhydrous minerals, and the general methods to infer the water content of the upper mantle through electrical anomaly revealed by MT.

Sol-gel Synthesized Yb-substituted ?-type Hexagonal Ferrites: Study of Structural, Grain Morphology, Electrical Polarization, Electrical Resistivity, Magnetic and Permeability Properties

In present work, an investigation was carried out about the various important properties of Yb 3+ substituted Potassium based ?-hexaferrite KFe 11-x Yb x O 17 (x= 0.0, 0.02, 0.06, 0.1). The Sol-gel auto combustion technique was used to synthesize all the samples. The X-ray diffraction (XRD) patterns confirmed the single hexagonal phase for all prepared samples. The Scanning Electron Microscopy (SEM) confirmed the agglomeration of small particles into big grains. The DC electrical resistivity, measured in the voltage range of (-200V) to (200V), was observed to vary with Yb 3+ contents. The Polarization versus electric field loops revealed the lossy behaviour of pure and substitute samples which indicated the resistive nature of the samples. The saturation and remanence polarization first decreased and then increased with Yb 3+ substitution due to ferric ions distribution between octahedral sites and resistive nature of the samples, respectively. The samples exhibited peculiar magnetic behaviour with the substitution of Yb 3+ ions. The saturation magnetization was increased up to concentration x = 0.06 and then decreased with further substitution of Yb 3+ contents. The coercivity values varied in the range of 141.43 to 279.26 Oe for all the samples which confirmed the soft magnetic nature of present synthesized material. The real part (µ’) and imaginary part (µ’’) of permeability exhibited the high values at low frequencies and these values decreased with the increase of frequency. The prepared samples were supposed to be used as core material of transformer and in high frequency applications due to high resistivity value and low eddy current losses.

Experimental study of electrical complex resistivity in a 2D multiphase porous medium under non‐isothermal conditions: Application to soil remediation monitoring

AbstractIn this decade, electro‐geophysical methods are widely used in different environmental subjects. Studies on soil remediation when polluted by dense non‐aqueous phase liquids (DNAPLs) has become a certain need for all countries. Geoelectrical methods have shown their potential to facilitate evaluating decontamination processes. Our challenge in this study was to understand how coupled temperature and saturation changes affect electro‐geophysical parameters in a contaminated 2D sample. The primary objective was to evaluate the efficiency and potential of spectral‐induced polarization (SIP) for monitoring the recovery of DNAPLs in contaminated porous media. A set of 2D tank experiments investigated the impacts of temperature and saturation changes on the electrical complex resistivity of a saturated porous medium under non‐isothermal conditions. The measurements were made with a coal‐tar and water fluid pair in a porous medium that has been simulated by 1 mm glass beads. Hot water was circulated around the tank and an immersion heater used to heat the porous medium in the tank at different stages. The SIP technique (also called complex resistivity) was used to measure the complex electrical resistivity of a medium in the frequency domain. The experimental results for a simple drainage case were validated using numerical modelling. The complex electrical resistivity was used to obtain the saturation field before and after imbibition. For this purpose, the generalized Archie's law obtained for the same fluid pair with 1D cells (with a vertical flow) was used. Our results from electrical resistivity measurements for saturation fields are in accordance with 2D tank images and can illustrate the saturation change with pointwise resistivity measurements. The results show that saturation change has the primary role in electrical resistivity variation compared to temperature (5%–7%). We also studied the effects of temperature change on the Cole–Cole parameters, and the results confirm our previous findings with the same variation trend in these parameters. The results from varying electrical complex resistivity from the 2D tank (with vertical and horizontal flow) in the laboratory conditions will help us to understand the coupled temperature and saturation effects on complex resistivity in a real polluted site case.

Relaxation processes in Al-R (R= Ce, Sm) glass-forming alloys

In present work, experimental studies of viscosity, density, and electrical resistivity of Al91Ce9 and Al90Sm10 glass-forming alloys are carried out. It is shown that these compositions are characterized by the presence of long-term processes of transition to a more homogeneous state (long-term relaxation).