Linear Polarization Measurements Research Articles

Hydraulic convey of iron ore slurry: Pipeline wear and ore particle degradation in function of pumping time

This paper reports and discusses the results of an experimental investigation on hydraulic transportation of iron ore concentrate and its effect on slurry wear, pure erosion and pure corrosion of a carbon steel pipe. For this, a specially designed test-loop was built to simulate long distance iron ore transportation, allowing also to determine pure erosion effects by means of a specially designed cathodic protection system. Pure corrosion damage was evaluated by linear polarization measurements in filtered ore concentrate, i.e., in the absence of particles. The results revealed that pure erosion and pure corrosion effects were much lower than the measured wear, evaluated as pipe thickness loss, indicating an important synergism between erosion and corrosion. Wear damage results in microcraters aligned in the flow direction, which merge with each other likely due to enhanced electrochemical activity fed by the erosion process. Evaluation of the effect of the pumping time on the ore concentrate characteristics revealed that particles sizes decreased while the sphericity factor increased leading to lower wear rates. Finally, a mechanism explaining the pipeline wear associating erosion, corrosion and the material microstructure as well as a methodology to forecast the pipelines thickness loss as a function of the ore concentrate travelling distance were also proposed.

Electrochemical Performance of Fe40Al-X (X = Cr, Ti, Co, Ni) Alloys Exposed to Artificial Saliva.

Fe–Al intermetallic compounds have been considered excellent candidates as alternative alloys for various applications in corrosive environments compared to other Fe-based alloys. Their excellent corrosion resistance is due to the development of an Al-based passive layer. The performance of the passive layer can be improved by adding a third alloy element. Therefore, in this study the electrochemical performance of the Fe40Al intermetallic alloy modified by the addition of a third alloy element (Cr, Ti, Co, Ni) is evaluated. The corrosion resistance of intermetallic alloys has been evaluated by electrochemical tests (potentiodynamic polarization curves, and measurements of open circuit potential, linear polarization and electrochemical impedance) in artificial saliva. The performance of intermetallic alloys was compared with that of Ti. The results obtained showed that the addition of Ni and Ti substantially improves the corrosion resistance of the base intermetallic. The corrosion resistance shown is comparable or greater than that shown by Ti. However, the addition of Co reduces the corrosion resistance of the base intermetallic.

Evidence for octupole collectivity in ^{172}{mathrm {Pt}}

Excited states in the extremely neutron-deficient nucleus ^{172}{mathrm {Pt}} were populated via ^{96}mathrm {Ru}(^{78}mathrm {Kr},2p) and ^{92}mathrm {Mo}(^{83}mathrm {Kr},3n) reactions. The level scheme has been extended up to an excitation energy of approx 5~hbox {MeV} and tentative spin-parity assignments up to I^pi = 18^+. Linear polarization and angular distribution measurements were used to determine the electromagnetic E1 character of the dipole transitions connecting the positive-parity ground-state band with an excited side-band, firmly establishing it as a negative-parity band. The lowest member of this negative-parity structure was firmly assigned spin-parity 3^-. In addition, we observed an E3 transition from this 3^- state to the ground state, providing direct evidence for octupole collectivity in ^{172}{mathrm {Pt}}. Large-scale shell model (LSSM) and total Routhian surface (TRS) calculations have been performed, supporting the interpretation of the 3^- state as a collective octupole-vibrational state.

Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A Measurement of Circular Polarization at 40 GHz

Abstract We report measurements of circular polarization from the first two years of observation with the 40 GHz polarimeter of the Cosmology Large Angular Scale Surveyor (CLASS). CLASS is conducting a multi-frequency survey covering 75% of the sky from the Atacama Desert designed to measure the cosmic microwave background (CMB) linear E and B polarization on angular scales 1° ≲ θ ≤ 90°, corresponding to a multipole range of 2 ≤ ℓ ≲ 200. The modulation technology enabling measurements of linear polarization at the largest angular scales from the ground, the Variable-delay Polarization Modulator, is uniquely designed to provide explicit sensitivity to circular polarization (Stokes V). We present a first detection of circularly polarized atmospheric emission at 40 GHz that is well described by a dipole with an amplitude of when observed at an elevation of 45°, and discuss its potential impact on the recovery of linear polarization by CLASS. Filtering the atmospheric component, CLASS places a 95% confidence upper limit of to on for , representing an improvement by two orders of magnitude over previous CMB limits.

Multi-quasiparticle excitations of 91Ru * * Supported by National Natural Science Foundation of China (U1632137)

The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni (36Ar, 2p1n ) 91Ru reaction at a beam energy of 111 MeV. Charged particles, neutrons, and -rays were emitted in this reaction and detected by the DIAMANT CsI ball, Neutron Wall, and the EXOGAM Ge clover array, respectively. In addition to the previously reported levels in 91Ru, new low-to-medium spin states were observed. Angular correlation and linear polarization measurements were performed to unambiguously determine spins and parities of the excited states in 91Ru. The low-spin states of 91Ru exhibit a scheme of multi-quasiparticle excitations, which is very similar to that of the neighboring isotone. These excitations have been interpreted in terms of the shell model. The calculations performed in the configuration space reproduce the experimental excitation energies reasonably well, supporting the interpretation of the newly assigned positive-parity states in terms of the three quasiparticle configurations and .

Efficiency of Organic Corrosion Inhibitors Derived from Thai-Bael Fruit Extract for Preventing Corrosion in Carbon Steels

The inhibiting action of Thai-bael fruit extract at room temperature on hot-rolled steel in 1M HCl solution was studied. The chemical functional groups of the green inhibitors were characterized by Fourier-transformed infrared spectroscopy. The electrochemical activities of steel surface were investigated through linear polarization measurements, electrochemical impedance spectroscopy, surface assessment techniques based on optical microscopy and X-ray absorption spectroscopy. Electrochemical testing samples have been prepared in the form of square plates with the size 1 × 1 cm2. The organic corrosion inhibitor extract from Thai-bael fruit has shown the smallest corrosion current density (Icorr) of 114.8 μA cm-2 and corrosion potential (Ecorr) of -424.6 mV, compared with standard Ag/AgCl electrode potential. In comparison, similar tests in the bare HCl solutions yielded Icorr = 882.4 mA cm-2 and Ecorr = -445.8 mV. The mixed-type corrosion inhibiting behaviour was evidenced in the results of the polarization measurements. Electrochemical impedance spectroscopy reveals that the resistance to charge transfer due to the presence of the extracts has been increased by about four times that of the same test on the bare HCl solution, indicating the formation of a protective layer. The adsorption of the organic molecules near the steel-electrolyte interface is evident in the decreasing double-layer capacitance with the enhancing concentration levels of the extract. This latter finding supports the displacement of the water molecules by means of the adsorption of the inhibitors on the steel surface. The optical images of steel surface before and after being immersed in HCl solution also showed pieces of evidence of corrosion retardation. XANES study as well as the linear combination fitting revealed that the samples immersed in HCl solutions with Thai-bael fruit extract possess less Fe3+ compositions. All tendencies across the four examinations indicate that Thai-bael fruit extract could potentially inhibit the corrosion reaction of steel electrodes in the acidic solution.

Multidirectional monolayer metal nano-grating micro polarizer array based on nanoimprint lithography and plasma ashing process

A novel fabrication process based on nanoimprint lithography (NIL) and plasma ashing process is proposed for the efficient fabrication of multidirectional monolayer metal nano-grating micro polarizer array (MPA). In this process, the NIL resist serves as a multifunction layer: the definition of the nano-grating patterns and the sacrifice layer for the monolayer metal nano-grating MPA forming. As a demonstration, a quartz filter with large area of monolayer metal nano-grating MPA was fabricated by this novel process. The performance test results demonstrate that the extinction ratios of the four tested micro polarizers with different orientations are 10.25, 10.45, 9.37, and 10.55, and the maximum polarization transmittances are 40.28%, 42.31%, 40.31%, and 42.35%, respectively. The polarization imaging experiment results demonstrate that the angle of polarization measurement error is <0.3°; the degree of linear polarization measurements error is <2.5%.

Simulating the Solar Corona in the Forbidden and Permitted Lines with Forward Modeling. I. Saturated and Unsaturated Hanle Regimes

Abstract The magnetic field in the corona is important for understanding solar activity. Linear polarization measurements in forbidden lines in the visible/IR provide information about coronal magnetic direction and topology. However, these measurements do not provide a constraint on coronal magnetic field strength. The unsaturated, or critical regime of the magnetic Hanle effect is potentially observable in permitted lines for example in the UV, and would provide an important new constraint on the coronal magnetic field. In this paper we present the first side-by-side comparison of forbidden versus permitted linear polarization signatures, examining the transition from the unsaturated to the saturated regime. In addition, we use an analytic 3D flux rope model to demonstrate the Hanle effect for the line-of-sight versus plane-of-sky (POS) components of the magnetic field. As expected, the linear polarization in the unsaturated regime will vary monotonically with increasing magnetic field strength for regions where the magnetic field is along the observer’s line of sight. The POS component of the field produces a linear polarization signature that varies with both the field strength and direction in the unsaturated regime. Once the magnetic field is strong enough that the effect is saturated, the resulting linear polarization signal is essentially the same for the forbidden and permitted lines. We consider how such observations might be used together in the future to diagnose the coronal magnetic field.

An HF Software‐Defined Radar to Study the Ionosphere

AbstractIn this paper, a novel design and implementation of a software‐defined high‐frequency ionospheric radar, the Penn State Ionospheric Radar Imager (PIRI), is described. Furthermore, preliminary results produced by the system (located at 40.71° N, 77.97° W) are presented. PIRI is designed to be a modest and low‐cost radar system, which is composed mostly of commercial‐off‐the‐shelf products and utilizing open‐source software to perform pulse generation, pulse coding, downconversion, data acquisition, and signal processing. It is designed to be mobile, as it can easily be deployed at temporary locations to study local ionospheric disturbances. For the results presented herein, the radar operating frequency was 5.125 MHz. However, as the system is software defined and short active receive antennas are used, only the transmit antenna needs to be changed to operate over the entire high‐frequency (HF) band. The two orthogonal receive antennas enable both linear and circular polarization measurements. Peak transmit power of the system is 500 W. PIRI is designed to be a modest and cost‐effective alternative to the current standard HF ionospheric sounding systems and can be readily replicated.

SPEX airborne spectropolarimeter calibration and performance.

To improve our understanding of the complex role of aerosols in the climate system and on air quality, measurements are needed of optical and microphysical aerosol. From many studies, it has become evident that a satellite-based multiangle, multiwavelength polarimeter will be essential to provide such measurements. Here, high accuracy (∼0.003) on the degree of linear polarization (DoLP) measurements is important to retrieve aerosol properties with an accuracy needed to advance our understanding of the aerosol effect on climate. SPEX airborne, a multiangle hyperspectral polarimeter, has been developed for observing and characterizing aerosols from NASA's high-altitude research aircraft ER-2. It delivers measurements of radiance and DoLP at visual wavelengths with a spectral resolution of 3 and 7-30nm, respectively, for radiance and polarization, at nine fixed equidistant viewing angles from -56° to +56° oriented along the ground track, and a swath of 7° oriented across-track. SPEX airborne uses spectral polarization modulation to determine the state of linear polarization of scattered sunlight. This technique has been developed in the Netherlands and has been demonstrated with ground-based instruments. SPEX airborne serves as a demonstrator for a family of space-based SPEX instruments that have the ability to measure and characterize atmospheric aerosol by multiangle hyperspectral polarimetric imaging remotely from a satellite platform. SPEX airborne was calibrated radiometrically and polarimetrically using Jet Propulsion Laboratory (JPL) facilities including the Polarization Stage Generator-2 (PSG-2), which is designed for polarimetric calibration and validation of the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI). Using the PSG-2, the accuracy of the SPEX airborne DoLP measurements in the laboratory setup is found to be 0.002-0.004. Radiometric calibration is realized with an estimated accuracy of 4%. In 2017, SPEX airborne took part in the "Aerosol Characterization from Polarimeters and Lidar" campaign on the ER-2 that included four polarimeters and two lidars. Polarization measurements of SPEX airborne and the coflying Research Scanning Polarimeter (RSP), recorded during the campaign, were compared and display root-mean-square (RMS) differences ranging from 0.004 (at 555nm) up to 0.02 (at 410nm). For radiance measurements, excellent agreement between SPEX airborne and RSP is obtained with an RMS difference of ∼4%. The lab- and flight-performance values for polarization are similar to those recently published for AirMSPI, where also an intercomparison with RSP was made using data from field campaigns in 2013. The intercomparison of radiometric and polarimetric data both display negligible bias. The in-flight comparison results provide verification of SPEX airborne's capability to deliver high-quality data.

Adsorptive, inhibitive and thermodynamics studies on the corrosion of mild steel in the presence of Mangifera indica gums

Abstract The adsorption and inhibitive behavior of gums obtained from Mangifera indica tree was investigated at 303-333 K using weight loss and linear polarization measurements. The results obtained from both measurements showed that Mangifera indica gums inhibited the corrosion of mild steel in 1.0 M HCl. Linear polarization measurements revealed Mangifera indica gums to inhibit both the anodic and cathodic reactions on the surface of the mild steel thereby functioning as a mixed-type inhibitor. Adsorption behavior of the gums were approximated by the isotherm models of Langmuir, Freundlich and Temkin. The adsorption mechanism derived from the trend in inhibition efficiency as a function of temperature as well as kinetic and activation parameters signified Mangifera indica gums adsorbed on the surface of the mild steel through the mechanism of physisorption and that the adsorption process was exothermic and spontaneous.

Angle of linear polarization images of outdoor scenes

Observations from the Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI) are used to relate angle of linear polarization (AoLP) measurements to material properties and illumination conditions in sunlit outdoor environments. GroundMSPI is a push-broom spectropolarimetric camera with an uncertainty in degree of linear polarization (DoLP) of ±0.005. This polarimetric accuracy yields useful AoLP images even when the DoLP is less than 0.02. AoLP images are reported with respect to dependency on surface texture, surface orientation, albedo, and illumination conditions. Agreement with well-known principles of polarized light scattering is illustrated, and several special cases are described. Expected observations of AoLP tangential to surface orientation and AoLP perpendicular to the scattering plane are reported. Significant changes in the AoLP are observed from common variations in outdoor illumination conditions. Also, simple variants in material properties change the dominant polarized light scattering process and thus the AoLP. Measurement examples that isolate a 90 deg AoLP flip are shown for a sunny and cloudy day as well as an object of high and low albedo.

Corrosion resistance of epoxy primer, polyurethane, and silyl acrylate anti-fouling on carbon steel

Anti-fouling paint is commonly applied as a protective coating on steel structures in the marine environment; one of the anti-fouling paint materials is silyl acrylate copolymer which can hydrolyse with seawater and form leaching layers to release biocide pigments. This study evaluates a three-layer paint comprised of epoxy primer, polyurethane, and silyl acrylate anti-fouling on carbon steel plates through polarization measurements and a salt spray test. Linear polarization measurements are carried out on an unscribed specimen with a potential range of -1.0 to 1.0 Volts. The salt spray test is conducted on scribed specimens, lasts 168 hours, and involves periodic visual observation. The polarization analysis shows pseudo-passive behavior in a system that represents, first, the less protective passive layer of primer and, second, the progressive erosion of a leaching layer of the anti-fouling paint which exposes a new layer beneath. The salt spray test shows that the three-layer paint has poor corrosion resistance in the atmospheric environment indicated by peeled layers and the occurrence of underfilm corrosion since the 48-hour test period.

Precision test of the weak equivalence principle from gamma-ray burst polarization

If the weak equivalence principle (WEP) is broken, the measured values of the parametrized post-Newtonian parameter $\gamma$ from photons with left- and right-handed circular polarizations should differ slightly, leading to the arrival-time difference of these two circular components. Thus, the polarization vector of a linearly polarized light may rotate during the propagation. The rotation angle of the polarization vector depends on both the photon energy and the distance of the source. It is believed that if the rotation angle differs by more than $\pi/2$ over an energy range, then the net polarization of the signal would be significantly suppressed and could not be as high as the observed level. Thus, the detection of highly polarized photons implies that the relative rotation angle ($\Delta\Theta$) should not be too large. In this paper, we give a detailed calculation on the evolution of gamma-ray burst (GRB) polarization arising from a possible violation of the WEP, and we find that more than $60\%$ of the initial polarization degree can be conserved even if $\Delta\Theta$ is larger than $\pi/2$. In addition, to tightly constrain the WEP violation, GRBs with harder spectra and polarization observations in a wider energy range seem to be favored. Applying our formulas to the measurements of linear polarization from GRB 110721A and GRB 061122, we obtain strict limits on the differences of the $\gamma$ values as low as $\Delta\gamma<1.3\times10^{-33}$ and $\Delta\gamma<0.8\times10^{-33}$. These provide the most stringent limits to date on a deviation from the WEP, improving at least 6 orders of magnitude over previous bounds.

Conversion Measure of Faraday Rotation–Conversion with Application to Fast Radio Bursts

Abstract Faraday rotation–conversion is the simultaneous rotation of all three Stokes polarization parameters, Q, U, and V, as an electromagnetic wave propagates through a magnetized plasma. In this regime, the Faraday plasma screen is characterized by more than just a rotation measure. We define the conversion measure that characterizes the wavelength-dependent conversion between the linear and circular polarization. In a cold plasma, the conversion occurs at the localized regions along the wave’s path, where the large-scale magnetic field is perpendicular to the propagation direction. We show that the number of these regions along the line of sight through the screen, and their individual contributions to the conversion measure, can be inferred from the polarization measurements. We argue that the simultaneous measurement of wavelength-dependent linear and circular polarization might give an important insight into the magnetic-field geometry of the Faraday screen in FRB 121102 and other repeating fast radio bursts.

Studies on Corrosion of Titanium and Air-Oxidized Titanium in Fluorinated Nitric Acid

Titanium (Ti) is a lustrous transition metal which possesses excellent corrosion resistance in several aggressive environments but is attacked by acidic fluoride media. In this work, the addition of fluoride ion to nitric acid on the corrosion behavior of Ti and air-oxidized Ti was studied. Air oxidation of Ti at 800 °C for 5 h resulted in the formation of an intact rutile TiO2 layer with a thickness of about 35 μm. The corrosion resistance was investigated from the polarization resistance (R_{text{P}}) values which were obtained from linear polarization and electrochemical impedance spectroscopy (EIS) measurements. A decrease in the R_{text{P}} value of Ti with the addition of fluoride ion in nitric acid was observed, and this indicated the formation of an unstable layer, which resulted in accelerated dissolution. The several order increase in the R_{text{P}} value of air-oxidized Ti in nitric acid containing fluoride ions pointed the improved resistance to corrosion. The diffusivity of species through the air-oxidized TiO2 layer was estimated from the electrochemical equivalent circuit (EEC) analysis of EIS data. Even though the diffusivity increased by several orders with the addition of fluoride ions, air-oxidized Ti provided better protection against nitric acid containing fluoride ions than Ti. The corrosion rates of Ti and air-oxidized Ti in boiling nitric acid containing fluoride ions were also estimated from weight loss experiments. Even in boiling fluorinated nitric acid, air-oxidized Ti provided better corrosion protection, with corrosion rates of about 1000 times less than that of Ti.

Corrosion Behavior of Noble Metals in Different Oral Media

In this first study, the corrosion behavior of the noble (Au, Pd, Rh, Cu, Ag, Pt, Ir) metals studied in 0.1M citric acid (CA), 10% carbamide peroxide (CP), artificial saliva (AS) and in the presence of CP, mouthwash (MW) and in presence of AS, and 0.1M NaCl solutions as oral solution. Electrochemical methods investigated with open circuit potential, impedance spectroscopy, current-potential and linear polarization measurements. Metal electrodes immersed in different oral solutions during a week for the determination of total metal cations. These cations analyzed by ICP-OES/MS. This article outline determined with corrosion tendencies of the noble metals and the amount of these ions passing through the human body. Scanning electron microscope (SEM) images showed that gold surface damaged in the presence of the CP. Additionally, the surface examined with EDS. It is concluded that the corrosion rate of noble metals increased in the presence of carbamide peroxide, due to the additional reactions pathways mediated by hydrogen peroxide anions. Keywords : Noble metals, Pilling-Bedworth, Hydrogen Peroxide, Artificial Saliva, Mouthwash DOI : 10.7176/JSTR/5-4-14

Kinetics and thermodynamics of the corrosion of mild steel in the presence of Euphobia tirucalli gums.

Understanding the mechanism of corrosion of steel in acidic environments along with the accompanying quest for corrosion inhibitors that are non-toxic to the environment is of significant industrial concern. This work sets to investigate the corrosion of mild steel in 1.0 M solution of HCl in the presence of Euphobia tirucalli gums using weight loss and linear polarization measurements. The study was carried out within the inhibitor concentration range of 0.2-1.0 and at the temperature range of 303 - 333 K. From the results obtained, it was observed that ET gums inhibited the dissolution of mild steel in the acid medium. Thermodynamic parameters obtained from the studies revealed the corrosion inhibition process to be spontaneous, exothermic and physisorptive. The adsorption of ET gums on the steel surface aligned well with the Langmuir, Fruendlich and Temkin isotherm models . Linear polarization results revealed that ET functioned as a mixed-type inhibitor by inhibiting both the cathodic and anodic reactions on the mild steel surface.

Potentiostatic studies of the influence of temperature on lead-silver anodes during electrowinning and decay period

ABSTRACTThe electrochemical behaviour of the Pb-0.7% Ag anode has been investigated in zinc sulphuric acid electrolyte containing 5, 8, 12 g/L Mn2+ by electrochemical measurements at different temperatures of 35°C, 40°C, 45°C. It was observed by cyclic voltammetry before electrolysis that temperature increase from 35°C to 45°C resulted in a decrease in the oxidation peak I (Pb → PbSO4) and an increase in the oxygen evolution peak II (2H2O → O2 + 4H+ + 4e). At 2.01 V/SHE, the current densities of Pb-0.7% Ag anode in sulphuric acid solution containing 8 g/L Mn2+ at 35°C, 40°C and 45°C increased from 26.5 at 35°C to 28.5 and 37.7 mA/cm2 at 40 and 45°C, respectively. In the presence of ZnSO4 addition to the sulphuric acid solution, the anodic current of oxygen evolution at 2.01 V/SHE decreased by ∼ 18% at 40°C. After 2 h of potentiostatic polarisation in the presence of zinc sulphate addition at 2.01 V/SHE, electrochemical Noise Measurements showed that the admittance (corrosion rate) of the Pb-0.7% Ag anode in the zinc electrolyte increased with the increase in temperatures during decay. This tendency was also confirmed by linear polarisation and impedance measurements.

Insights from corrosion current measurements on corrosion mechanisms in reinforced concrete and on the evaluation of other corrosion data

During the past years Tafel polarization measurements have been implemented into the scope of measurements of CITec corrosion diagnosis projects. This has created a vast database of different and corresponding corrosion parameters, such as chloride and water content in the rebar vicinity, open circuit potential, electrolyte resistance, polarization resistance (from galvanostatic pulse and linear polarization) and corrosion current from Tafel polarization measurements. Although general limitations in using these methods on macro cell systems such as reinforced concrete are known, the comparative assessment of these data has led to a better understanding of the corrosion behaviour and of specific circumstances of the structures which deviated partly from usual expectations. For instance, a low polarization resistance at high chloride content will not result necessarily in a high corrosion current, if the reinforcement in the wider vicinity of the test location is similar active, and cathodic rebar areas are either very distant or retarded by very wet concrete. So the extended range of corrosion testing gives a more precise evaluation of the corrosion situation and permits a tailored repair and maintenance concept to be found. It has also been found that the Stern-Geary equation which is often used to calculate corrosion current densities and material loss of the reinforcement from linear polarization (LPR) measurements, doesn’t seem very feasible if used on reinforced concrete structures, as there appears to be a dominant influence of macro cell corrosion over the corrosion model of a homogenous mixed electrode (for which the Stern-Geary equation applies), and the true corrosion current densities may be either larger or (very often) much smaller than those calculated from Stern-Geary. This is not a new observation, and the findings will be discussed for several project cases.