Shot Noise Analysis Research Articles

Identification of carbonation‐induced corrosion of steel in concrete by electrochemical testing

AbstractCarbonation‐induced corrosion of steel in concrete can allow for premature degradation of structures. Corrosion probes in health monitoring systems can assess concrete carbonation and steel corrosion rates. The electrochemical noise (EN) technique has advantages for corrosion sensing. Instrumented concrete columns were fitted with a carbonation chamber for accelerated testing. EN was assessed through statistical evaluation of noise time signatures, noise resistance, and spectral analysis. The mean noise potential for the electrodes showed electronegative potential and correspondingly high rms noise current, indicative of corrosion activation in carbonated concrete. The estimated corrosion rates obtained from the noise impedance were comparable to those resolved from the polarization resistance and noise resistance. The shot noise analysis indicated isolated spontaneous noise events associated with the activation of local steel anodes. The outcomes of the testing indicate that the placement of low‐cost sensors and passive EN measurements can be used to monitor the onset of carbonation‐induced corrosion of steel in concrete and provide estimates on corrosion rates.

Shot Noise Analysis for Differential Sampling in Indirect Time of Flight Cameras

Continuous wave Time of Flight cameras obtain depth images by emitting a modulated continuous light wave and measuring the delay of the received signal. One of the main sources of error is shot noise. In this letter we analyze and provide insights about the effect of shot noise when obtaining the phase delay with a new architecture, based on differentiating the phase integrations in the analog domain, and using any number of points in the calculation of the Discrete Fourier Transform (DFT). One of the main findings is that the error depends on the integration time regardless the number of points in the DFT used to calculate the phase offset. Simulated experiments are provided which support the proposed theoretical analysis.

Corrosion monitoring method of 304 stainless steel in a simulated marine–industrial atmospheric environment: electrochemical noise method

PurposeThis paper aims to study the use of electrochemical noise (EN) technology in the corrosion continuous monitoring of stainless steel (SS) in an atmospheric environment.Design/methodology/approachAn EN electrode was designed and fabricated to acquire the EN of 304 SS in the atmospheric environment. The statistical analysis and shot noise analysis were used to analyze the EN, and the surface morphology analysis of 304 SS was used to verify the EN analysis results.FindingsThe activation state, passive film formation and pitting corrosion of 304 SS can be clearly distinguished by the amplitude and frequency change of EN. The metastable pitting corrosion and steady-state pitting corrosion can be identified with the shot noise parameters q and fn. Under the existence of chloride ion, the stability of 304 SS passive film decreases and the steady-state corrosion pits of 304 SS are more likely to form with the reduction of thin electronic layer (TEL) pH. The critical TEL pH of 304 SS corrosion is a pH between 3 and 4.Originality/valueIn an atmospheric environment, the EN technology was used in the corrosion continuous monitoring of SS.

Assessment of durability and zinc activity of zinc-rich primer coatings by electrochemical noise technique

The three-coat system consisting of a zinc-rich primer, epoxy midcoat, and polyurethane topcoat has been widely adopted for corrosion protection of structural steel bridges. Corrosion mitigation is afforded by the barrier characteristics of the various layers as well as beneficial galvanic coupling of the zinc pigments in the primer to the steel substrate when subjected to corrosive environments such as with moisture ingress and coating defects. The dispersed zinc pigments in the binder require adequate electronic coupling in order to provide the beneficial electrochemical coupling of the zinc to the steel. The application of the electrochemical noise (EN) technique to identify coating corrosion performance was reviewed in controlled laboratory tests. Zinc pigment activation and transition to passive-like conditions in defect and defect-free coating specimens could be identified by EN. The characteristic charge of noise events resolved by shot noise analysis was demonstrated to be related to anodic polarization of extended active zinc pigments adjacent to coating defect sites galvanically coupled to the exposed steel and passivated zinc pigments. Electrochemical noise resistance was shown to convey zinc/steel interfacial behavior in cases with sufficient activity but largely reflects coating barrier quality for intact coatings.

Auto- versus Cross-Correlation Noise in Periodically Driven Quantum Coherent Conductors.

Expressing currents and their fluctuations at the terminals of a multi-probe conductor in terms of the wave functions of carriers injected into the Fermi sea provides new insight into the physics of electric currents. This approach helps us to identify two physically different contributions to shot noise. In the quantum coherent regime, when current is carried by non-overlapping wave packets, the product of current fluctuations in different leads, the cross-correlation noise, is determined solely by the duration of the wave packet. In contrast, the square of the current fluctuations in one lead, the autocorrelation noise, is additionally determined by the coherence of the wave packet, which is associated with the spread of the wave packet in energy. The two contributions can be addressed separately in the weak back-scattering regime, when the autocorrelation noise depends only on the coherence. Analysis of shot noise in terms of these contributions allows us, in particular, to predict that no individual traveling particles with a real wave function, such as Majorana fermions, can be created in the Fermi sea in a clean manner, that is, without accompanying electron–hole pairs.

Laboratory-Scale Identification of Corrosion Mechanisms by a Pattern Recognition System Based on Electrochemical Noise Measurements

Uniform corrosion, pitting corrosion and passivation of 304 stainless steel were promoted and pattern recognition system (PRS) based on electrochemical noise (EN) measurements was employed to classify these corrosion mechanisms in laboratory-scale. The EN signals were analyzed using statistical, shot noise, wavelet and recurrence quantification analysis. It was found that the PRS designed by combining these EN parameters has a discriminant accuracy of 99.7%, which is superior to those designed by solely statistical parameters (92.4%), and the parameters selected by principle component analysis (97.8%). The application of the PRS above is evaluated by considering environmental factors and material types.

Electronic conduction during the formation stages of a single-molecule junction

Single-molecule junctions are versatile test beds for electronic transport at the atomic scale. However, not much is known about the early formation steps of such junctions. Here, we study the electronic transport properties of premature junction configurations before the realization of a single-molecule bridge based on vanadocene molecules and silver electrodes. With the aid of conductance measurements, inelastic electron spectroscopy and shot noise analysis, we identify the formation of a single-molecule junction in parallel to a single-atom junction and examine the interplay between these two conductance pathways. Furthermore, the role of this structure in the formation of single-molecule junctions is studied. Our findings reveal the conductance and structural properties of premature molecular junction configurations and uncover the different scenarios in which a single-molecule junction is formed. Future control over such processes may pave the way for directed formation of preferred junction structures.

Evaluation of the Effect of Molybdenum on the Pitting Corrosion Behavior of Austenitic Stainless Steels Using Electrochemical Noise Technique

Electrochemical noise (EN) studies were conducted on three austenitic stainless steels (SSs) with different molybdenum contents, 0.02 wt% Mo (Type 304LN SS), 2.53 wt% Mo (Type 316LN SS), and 3.58 wt% Mo (Type 317LN SS), in 0.01 M FeCl3 solution at the corrosion potential (Ecorr) and at a sampling frequency of 1 Hz. The EN data were analyzed using shot noise and wavelet analysis techniques. Current transient analysis showed that the total number of current transients, as well as transients with high current amplitude, decreased with increase in Mo content indicating increased resistance to pitting corrosion. Shot noise analysis revealed higher normalized characteristic charge (q)N at low frequency in Type 304LN SS as compared to Type 316LN SS and Type 317LN SS, implying increase in pitting corrosion resulting from the absence of Mo in this steel. Pit current decreased substantially with increase in Mo content. These results were supported by the standard deviation of partial signal (SDPS) values generated ...

Correlation of Electrochemical Noise Parameters with Degree of Sensitization in AISI Type 316LN Stainless Steel

Degree of sensitization in 316LN stainless steel (SS) specimens sensitized at 898, 923 and 948 K for 500 h was obtained using double loop electrochemical potentiokinetic reactivation (DLEPR) technique as 7.4, 14.5 and 9.3% respectively. The sensitized specimens were pulsed polarized so that only Cr-depleted regions of the sensitized grain boundaries contributed to the electrochemical noise (EN) study. The DOS values evaluated from DLEPR technique were correlated with the EN parameters viz. standard deviation of current, σI and characteristic charge, q and characteristic frequency, fn, obtained from shot noise analysis in order to assess the extent of intergranular corrosion (IGC) attack in 316LN SS. The plot of σI versus time showed highest σI values for the specimen sensitized at 923 K for 500 h, indicating high grain boundary dissolution and hence, severe IGC attack, whereas the specimen sensitized at 898 K for 500 h showed the least σI values indicating lower dissolution and least IGC attack. 316LN SS specimen heat-treated at 948 K for 500 h showed intermediate grain boundary dissolution rate. The charge q, determined from σI versus time plot showed a good correlation (>99%) with the DOS values obtained from DLEPR experiments. The power spectral density values of the current signal in the frequency independent region were found to have excellent correlation with these observations. The above findings were further supported by scanning electron microscopic examination which showed an increase in grain boundary width in the sensitized specimens when the heat-treatment temperature was raised from 898 to 923 K and on further increasing the temperature to 948 K, a marginal decrease in the grain boundary width was observed.

Shot Noise Analysis to Investigate the Corrosion Inhibition of AZ91D Magnesium Alloy in Sulfuric Acid Solution

The corrosion inhibition of AZ91D magnesium alloy in 0.01 M H2SO4 by a Schiff base compound was investigated using Potentiodynamic polarization, Electrochemical Impedance Spectroscopy and Electrochemical Noise methods. It is found that the Schiff base acts as mixed-type inhibitor and the inhibition efficiency increases with concentration. Electrochemical impedance spectroscopy results showed that the Schiff base acts by adsorption at the metal/solution interface. Shot noise analysis showed that the inhibitor addition decreases the number of charge transfer events instead of the value of charge transfer at each electrochemical corrosion event. The corrosion inhibition effect was approved by suitable surface analysis.

Effect of nitrogen on corrosion behaviour of 304LN SS in nitric acid and simulated high level waste by electrochemical noise

The effect of nitrogen on the corrosion resistance of 304LN SS containing 0.132, 0.193 and 0.406 wt-% N was investigated in 1M, 4M and 8M nitric acid and simulated high level waste (HLW) using electrochemical noise (EN) technique. Statistical, spectral, shot noise and wavelet methods were employed for EN analysis. Noise resistance and spectral noise resistance increased, while characteristic frequency decreased with increase in nitrogen content, implying lower corrosion activity with increase in nitrogen content. The cumulative probability plots obtained from shot noise analysis showed a shift towards lower frequency with increase in nitrogen content, and toward higher frequency with increase in concentration of nitric acid. Wavelet analysis of current noise was used for deriving mechanistic information. Micro laser Raman studies were carried out for passive film analysis. The results are detailed in the manuscript.

Shot noise variation within ensembles of gold atomic break junctions at room temperature

Atomic-scale junctions are a powerful tool to study quantum transport, and are frequently examined through the mechanically controllable break junction technique. The junction-to-junction variation of atomic configurations often leads to a statistical approach, with ensemble-averaged properties providing access to the relevant physics. However, the full ensemble contains considerable additional information. We report a new analysis of shot noise over entire ensembles of junction configurations using scanning tunneling microscope-style gold break junctions at room temperature in ambient conditions, and compare these data with simulations based on molecular dynamics, a sophisticated tight-binding model, and nonequilibrium Green's functions. The experimental data show a suppression in the variation of the noise near conductances dominated by fully transmitting channels, and a surprising participation of multiple channels in the nominal tunneling regime. Comparison with the simulations, which agree well with published work at low temperatures and ultrahigh vacuum conditions, suggests that these effects likely result from surface contamination and disorder in the electrodes. We propose additional experiments that can distinguish the relative contributions of these factors.

The reliability of electrochemical noise and current transients characterizing metastable pitting of Al–Mg–Si microelectrodes

Current transient measurements and electrochemical noise (EN) method have been used to characterize the metastable pitting events for Al–Mg–Si microelectrodes (diameter 50μm) in deaerated neutral 0.5M NaCl solution. The results are compared with those obtained by atom force microscopy and scanning electron microscopy. The pit numbers determined by shot noise analysis at open circuit potential and by current transient analysis at −1.2V (SCE) are both significantly less than those determined by corrosion morphology image analysis. These results indicate that larger discrepancies can be introduced if the anodic and cathodic reactions localize severely on the same electrode.

Shot Noise analysis of subthreshold membrane potential activity in neurons

Shot noise is one of the most extensively harnessed phenomena used to model different aspects of neural activity in neuroscience. Shot noise processes [1] display very characteristic fluctuations that correspond to the sum of causal system responses to unitary event arrivals that follow a Poisson distribution. In general, applications of shot noise [2-4] have been confined to the so-called Campbell Limit corresponding to steady-state regime, or to specific post-synaptic responses that make the process Markovian or with the assumption of homogeneous Poisson event arrivals. In this work we go beyond this context to show that the shot-noise formalism can be used to analyze the synaptic activity of neurons beyond the Campbell limit, for any type of bounded post-synaptic response function and non-homogeneous Poisson event arrivals. This enhancement of technique allows for two main applications. 1) Computation of the full density for current synapses and statistical moments for conductance synapses. This yields a statistical description of the subthreshold membrane potential. This includes considering distributions on the afferent populations over biological parameters such as peak intensity, number of independent channels, or dynamical parameters such as distribution of incoming firing rate or variable incoming firing rate. The picture obtained is of particular interest for various applications such as calculating the transfer function. 2) Under stationarity assumptions, this technique offers the potential to reverse the moments of membrane potential integration. This offers a candidate method to infer characteristics of the synaptic activity (and therefore of the network activity) from the analysis of the subthreshold variations of the membrane potential. This application is of particular interest for the analysis of intracellular recordings in vivo. We illustrate these techniques by comparing analytic expressions with numerical estimates, as well as to neurons subject to a large range of synaptic activity (including low release rate far from the diffusion limit). In conclusion, due to their flexibility as a modeling tool, shot noise analysis appears as a very useful tool in computational neuroscience to model post-synaptic and sub-threshold membrane potential responses to incoming network activity, and also as a tool for electrophysiological analysis of network activity from intracellular recordings.

Analysis of shot noise in the detection of ultrashort optical pulse trains

We present a frequency domain model of shot noise in the photodetection of ultrashort optical pulse trains using a time-varying analysis. Shot-noise-limited photocurrent power spectral densities, signal-to-noise expressions, and shot-noise spectral correlations are derived that explicitly include the finite response of the photodetector. It is shown that the strength of the spectral correlations in the shot noise depends on the optical pulsewidth, and that these correlations can create orders-of-magnitude imbalance between the shot-noise-limited amplitude and phase noise of photonically generated microwave carriers. It is also shown that only by accounting for spectral correlations can shot noise be equated with the fundamental quantum limit in the detection of optical pulse-to-pulse timing jitter.

Shot noise analysis on corrosion behavior of zinc alloy (ZnAl4Cu1) under dry-wet cycles

The corrosion behaviors of zinc alloy (ZnAl4Cu1) in 3.5% (mass fraction) NaCl, 7.3% (mass fraction) Na2SO4 and simulated acid rain solutions were investigated using electrochemical measurements. The potential noise during dry-wet cycle was monitored and analyzed by fast Fourier transform (FFT), fast wavelet transform (FWT), shot noise theory and stochastic theory. Cumulative probability curves of event frequency fn indicate that the corrosion events in the dry cycles are greater than those in the wet cycles. Uniform corrosion was observed in the NaCl solution compared with more localized corrosion in the Na2SO4 solution, which is evidenced by FWT and SEM. Conditional events generation rate r(t) for diffusion controlled reactions decreases with increasing the time. r(t) values for uniform corrosion and diffusion controlled process are the largest in the wet cycle in 3.5% NaCl solution. The values of r(t) for pitting corrosion in Na2SO4 solution are observed to become large during spraying periods, and r(t) for pitting corrosion has the largest value in the Na2SO4 solution. The intergranular corrosion of zinc is serious in simulated acid rain solution.

STATISTICAL STUDY OF BIVALVE HIGH FREQUENCY MICROCLOSING BEHAVIOR: SCALING PROPERTIES AND SHOT NOISE ANALYSIS

We consider bivalve (oyster) behavior using high frequency valvometry data. These data are obtained in the field in the Arcachon bay, with light-weight electrodes of millimeters size, attached to the molluscs, and linked by flexible wires to an electronic control unit which measures valve activity. The latter are able to move freely and open their valve with an amplitude which is linked to environmental and physiological conditions, in order to filter surrounding waters. We consider here daily data recorded every 0.1 sec for 16 different animals, corresponding to a total of 1 728 000 data points. Valvometry data show important intermittent activity at high frequency, with frequent and sudden "microclosing" events (meaning partial closures), at apparently random times and with random amplitudes. The overall frequency spectrum of valve opening time series show power-law behavior with a slope β = 1.6 ± 0.1. The random succession of closing events with random amplitudes suggests to consider a shot-noise analysis, with two independent stochastic processes representing respectively the times of these discrete shot noise events and their amplitudes. This shows that methods and approaches devoted to extreme values, chaotic dynamics, recurrence time statistics in geosciences and climate studies can also be used to study living organisms and their interactions with complex environments such as their local ecosystem.

Analysis of Shot Noise at Finite Temperatures in Fractional Quantum Hall Edge States

We investigate shot noise at {\it finite temperatures} induced by the quasi-particle tunneling between fractional quantum Hall (FQH) edge states. The resulting Fano factor has the peak structure at a certain bias voltage. Such a structure indicates that quasi-particles are weakly {\it glued} due to thermal fluctuation. We show that the effect makes it possible to probe the difference of statistics between $\nu=1/5,{}2/5$ FQH states where quasi-particles have the same unit charge.Finally we propose a way to indirectly obtain statistical angle in hierarchical FQH states.

Influence of solution-annealing and stress-relieving on the pitting corrosion resistance of modified 316N SS weld metals: A study using EN technique

This paper presents the pitting corrosion resistance of AISI 316LN SS Weld joints in the (i) as-welded and (ii) post-weld heat-treated condition. The weld metal contains 0.055% carbon and 0.13% nitrogen in order to have improved creep strength. The welded components are subjected to (i) solution annealing at 1050 °C, (ii) stress relieving at 750 °C or (iii) dimensional stabilization at 550 °C depending upon the fabrication route. These welds are exposed to marine/coastal environment at various stages of fabrication, inspection, storage and commissioning after these heat-treatments, which may lead to pitting corrosion. Hence an attempt was made to understand the influence of microstructural change arising due to the post-weld heat-treatments on the susceptibility of these materials to pitting corrosion. Potentiodynamic polarisation as well as electrochemical noise (EN) studies were conducted in 0.5 M sodium chloride solution in open atmosphere. Shot-noise analysis, Weibull probability plots and the 3 dimensional plots using shot-noise parameters were used to assess the susceptibility to pitting corrosion. It has been established that solution annealing improves the pitting corrosion resistance whereas stress relieving as well as dimensional stabilization heat-treatments make the weld joints more prone to pitting. The localized corrosion resistance was correlated to the microstructural changes resulted during the various heat-treatments.

Assessment of intergranular corrosion (IGC) in 316(N) stainless steel using electrochemical noise (EN) technique

In the present work, an attempt was made to demonstrate the use of electrochemical noise (EN) technique in assessment of intergranular corrosion (IGC) in 316(N) stainless steel (SS). Degree of sensitization (DOS) in the specimens aged at 923 K for 24, 40, 50 and 100 h was determined using double loop electrochemical potentiodynamic reactivation (DLEPR) technique. Immediately after applying a prior preconditioning treatment, current and potential noise measurements were made. The DOS was determined from standard deviation of current noise ( σ I) versus time plot and it was found to bear a good correlation with the values obtained by DLEPR. Shot noise analysis of the EN data confirmed the above results.