Rate Of Conductivity Increase Research Articles

Annular flexible eddy current array (A-FECA) sensor for quantitative monitoring of cracks in ferromagnetic steels under varying loads and temperatures

In this study, we investigated an annular flexible eddy current array sensor for quantitative monitoring of cracks in ferromagnetic steels under varying loads and temperatures. First, the sensor was designed to monitor the length of cracks in ferromagnetic materials. Using numerical simulations, the effects of permeability, lift-off distance, and conductivity on the response of the sensor were studied. Simulation results showed that when the rate of increase in conductivity and the decrease in permeability were the same, it had the same effect on the trans-impedance response of the sensor. Based on this relation, a new sensor with a reference channel was proposed. At the same time, a new signal, ΔP, for ferromagnetic materials was defined to improve sensitivity to the cracks and to remove the influence of temperature variations. Then, simulated crack-monitoring experiments were carried out to verify the sensitivity of the new sensor. The results showed that the sensitivity of the new sensor improved more than three times that of the original. Moreover, to verify the temperature-compensation capability of the new sensor, a temperature experiment was carried out. When the ambient temperature increased from −20 °C to 70 °C, the ΔP signal remained almost unchanged, which did not affect the monitoring of cracks. Subsequently, quantitative monitoring of cracks in a ferromagnetic steel structure under varying loads was performed. Varying the load was found to change the permeability of ferromagnetic materials, which can result in fluctuations of the output signals. Because of the higher sensitivity of the optimized sensor, the sensor can achieve quantitative monitoring of cracks under various loads. Finally, a crack-monitoring experiment under environmental temperature interference was carried out. The sensor could provide quantitative monitoring of the cracks in ferromagnetic steels under varying environmental temperatures and loads.

Migration of impurity level reflected in the electrical conductivity variation for natural pyrite at high temperature and high pressure

This report presents the variations of the electrical conductivity and the migration of natural pyrite impurity levels at temperatures range from 298 to 573 K and pressures range from 1 atm. to 20.9 GPa. The electrical conductivity increases with temperature at a fixed pressure, displaying the semiconductor behavior of the sample. In spite of the positive correlations of electrical conductivity and pressure, there exists an acceleration in the rate of conductivity increase after ~13 GPa. No indication of a chemical reaction or structural phase transition of pyrite was detected by Raman spectroscopy. The main trace elements that affect the electrical properties of pyrite are determined by inductively coupled plasma with mass spectrometry (ICPMS). The transport activation energy of natural pyrite is ~0.045 eV at ambient pressure, which corresponds to the activation of the CoFe donor level (~1/2 E D), and decreases with increasing pressure.

Decomposition of chloroform and succinic acid by ozonation in a suction-cavitation system: Effects of gas flow

Abstract The conductivity of aqueous solutions containing 1 mM chloroform increases upon the chloroform decomposition that is induced by hydrodynamic cavitation in the suction-cavitation system. However, the rate of increase in conductivity (RIC) drops significantly, from 1.314 μS cm −1 min −1 without gas flow to 0.552 μS cm −1 min −1 with 25 mL min −1 of air flow. The RIC decreases further with increasing air flow, until pseudo-zero growth is reached at 200 mL min −1 air flow. Introducing O 3 at 33 mL min −1 gas flow (effective cavitation) improves RIC, from 0.4193 to 0.5509 μS cm −1 min −1 , but the enhanced rate (31.4%) is lower than at 200 mL min −1 of gas flow (little effective cavitation). The concentrations of dissolved O 2 , O 3 and H 2 O 2 , that is formed on-site, increase with increasing gas flow and orifice plate hole diameter. Succinic acid (0.42 mM) is not oxidized by O 3 or H 2 O 2 alone, but is rapidly degraded by a combination of O 3 /H 2 O 2 in the suction-cavitation system. The degradation rate of zero-order kinetics increases from 2.604 to 4.788 μM min −1 as orifice diameter increases from 5 to 8 mm. Increasing O 3 gas flow and temperature favor SA degradation. Increasing H 2 O 2 concentration is more effective in producing OH radicals and promoting the oxidation of succinic acid than increasing O 3 input amount.

Temperature dependent electrical conductivity of CNT–PEEK composites

The effect of temperature on electrical conductivity of nanocomposites consisting of Chemical Vapor Deposition (CVD)-grown multi-walled Carbon Nanotube (MWCNT) and Poly Ether Ether Ketone (PEEK) is presented in this paper. Different weight percentages of carbon nanotubes (CNT) were dispersed in PEEK through shear mixing by calendaring technique in Brabender. Percolation limit of the system was measured and discussed. The resulting nanocomposites were molded into round shaped pieces of 25.4 mm diameter and 1.4 mm thickness. The samples were then heated from room temperature to 140 °C while electrical conductivity is measured. It is found that electrical conductivity increases significantly with the increase in temperature and the rate of increase in conductivity with temperature depends on the content of CNT. The change in electrical conductivity does not follow the same route for heating and cooling cycle, thus resulting in electrical hysteresis.

Eosinophil major basic protein increases membrane permeability in mammalian urinary bladder epithelium.

The eosinophil granule protein major basic protein (MBP) is toxic to a wide variety of cell types, by a poorly understood mechanism. To determine whether the action of MBP involves an alteration in membrane permeability, we tested purified MBP on rabbit urinary bladder epithelium using transepithelial voltage-clamp techniques. Addition of nanomolar concentrations of MBP to the mucosal solution caused an increase in apical membrane conductance only when the voltage across the apical membrane was cell interior negative. The magnitude of the MBP-induced conductance was a function of MBP concentration, and the rate of the initial increase in conductance was a function of the transepithelial voltage. The MBP-induced conductance was nonselective for K+ and Cl-. Mucosal Ca2+ reversed the induced conductance, whereas mucosal Mg2+ partially blocked the induced conductance and slowed the rate of the increase in conductance. The induced conductance was partially reversed by changing the voltage gradient across the apical membrane to cell interior positive. Prolonged exposure resulted in an irreversible loss of the barrier function of the urinary bladder epithelium. These results suggest that an increase in cell membrane ion permeability is an initial step in MBP-induced loss of barrier function.

Room temperature high conduction state in annealed Ca-substituted yttrium iron garnet films

It was discovered that the application of a constant DC field (/spl sim/10/sup 4/ V/cm) at room temperature for several days reversed the changes in the electrical properties produced by thermal annealing in Ca:YIG single crystal films. The electrical conductivity of these films improved by five to seven orders of magnitude during this process to values as much as ten times greater than those of the as-grown state. After the field was removed this new high conduction state was found to be stable. The rate of conductivity increase became exponentially smaller when either the applied field or the temperature were decreased.

An anomalous conduction phenomenon in the Zn1−xFeCrO4Nixsystem

Abstract D.c. conductivity measurements carried out on ZnFeCrO4 have revealed a new conduction phenomenon. It was found that for temperatures above 360 K conduction is similar to that of semiconductors, obeying the relationship σ=σ0 exp (–E a/kT). At temperatures below 360 K, a transition occurs and the conductivity starts to increase with decreasing temperature. The rate of increase in conductivity is neither linear, as for metallic behaviour, nor abrupt, as for superconductors, but increases exponentially. The gradual replacement of Zn with Ni reduces this anomalous conduction phenomenon, until it completely disappears when all the Zn has been replaced by Ni.

The electrical breakdown of cell and lipid membranes: the similarity of phenomenologies

The current responses of human erythrocyte and L-cell membranes being subject to rectangular voltage pulses of 150–700 mV amplitude and 5·10 −3-10 s duration were recorded by means of the patch-clamp method. The behaviour of planar lipid bilayer membranes of oxidized cholesterol and UO 2+ 2-modified bilayers of azolectin in a high electric field was investigated for comparison. The gradual growth in the conductance (reversible electrical breakdown) was found for both the cell membranes and lipid bilayers of the compositions studied, with the application of voltage pulses of sufficient duration, to be completed by its drastic enhancement (irreversible breakdown). The time interval preceding the irreversible breakdown and the rate of increase in conductance during the reversible breakdown are determined by the amplitude of the voltage applied. The recovery of the initial properties of the membrane following the reversible breakdown consists of the two stages, the latter substantially differing by their characteristic times. The first very rapid stage ( τ ⪡ 1 ms) reflects the lowering of the conductance of small pores with decreasing voltage across the membrane. The diminishing of the number and mean radii of the pores resulting in their complete disappearance occurs only at the second stage of membrane healing, which lasts several seconds or even minutes. The phenomenological similarity of the cell and lipid membrane breakdown indicates that pores developed during the electrical breakdown of biological membranes arise in their lipid matrices. The structure and the properties of the pores are discussed.

Conductivity through Hydrogen Bonded Organic Compounds and Their Homogeneous Solutions: II . Conductivity of Phenol, o‐ and p‐nitrophenol in Benzene and Ether

The conductivity of p‐nitrophenol is more than that of o‐nitrophenol in ether at 21°C. The solvent effect on conductivity is shown by measuring the conductivity of phenol in benzene and in ether at 21°C. The participation of the hydrogen‐bonded complex in the conductivity of the system is postulated. Such complexing lowers the rate of increase in conductivity with concentration of phenol in ether compared to that in benzene.

Effect of Hydrogen and Carbon Monoxide on the Electrical Conductivity of Zinc Oxide

Abstract The rate of increase in conductivity of zinc oxide caused by hydrogen was found to be proportional to p0.85 and to have an activation energy of 21 kcal./mol. For this system the activation energy of the increase of donors was shown to be almost the same as that of the conductivity increase. The activation energy of the decrease of donors by evacuation was 31 kcal./mol. A similar conductivity increase was observed with carbon monoxide. On the basis of these results together with those of adsorption measurements reported previously, it was concluded that the conductivity increase was scarcely related at all to the hydrogen chemisorption, indicating that it is untenable to postulate two such types of hydrogen chemisorption as was believed in the previous work, i.e., one responsible for the conductivity increase and the other without such effect. As for the cause of the conductivity increase, the surface reduction of zinc oxide was suggested.