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The effect of undissociated acetic acid on the integrity of an iron carbonate (FeCO3) layer formed on platinum and X65 steel substrates is investigated. Experiments were conducted using buffered solutions with 0.8 mM to 5 mM undissociated acetic acid. For the platinum substrates, changes in the FeCO3 layer were monitored via in situ electrochemical quartz crystal microbalance (EQCM) measurements. This investigation was supported by performing electrochemical experiments, under comparable conditions, on the X65 steel specimens, linking the integrity of FeCO3 layer to its corrosion protection effect. The EQCM measurements revealed that the addition of acetic acid, at all concentrations tested here, caused partial dissolution of the FeCO3 layer. The dissolution occurred selectively, with the outer layer dissolving first, leaving behind an inner FeCO3 layer at the end of the immersion experiment. The electrochemical results revealed that introducing the acetic acid caused a sudden increase in the corrosion rate, which over time returned to a lower value similar in magnitude to that seen before addition of the acetic acid. This was attributed to the protection provided by the inner FeCO3 layer, which was only mildly affected by the addition of acetic acid and was able to repair over time. It was proven that the dissolution of the protective FeCO3 layer in the presence of acetic acid was not due to a small pH change but rather due to the formation of ferrous acetate complexes and changes in ionic strength, which decreases the FeCO3 saturation values.

In this paper, we introduce a robust framework for linear regression–based channel estimation (CE) designed for multipath channel environments within a new radio (NR) sounding reference signal (SRS) system. The main contribution of this study is to show that integrating channel impulse response (CIR) refinement with existing CE schemes significantly improves CE performance in terms of normalized mean squared error (NMSE). Specifically, our approach employs thresholding-based CIR refinement to eliminate noise tap components effectively, discern the lengths of dominant tap elements, and augment linear regression–based CE’s efficacy. Specifically, it is shown that increasing the number of channel taps for threshold setting further enhances the performance of regression–based CE by leveraging CIR refinement. By utilizing an optimized threshold design, our results reveal close performance compared to both ideal tap information-based regression and the theoretical performance of linear minimum mean square error (LMMSE) estimation, whose findings are substantiated by numerical analyses employing our proposed polynomial regression–based channel estimation (PRCE) and DFT regression–based channel estimation (DRCE) schemes.

Rapid industrialization has significantly influenced people’s lifestyles in the recent decades, and the influence of traditional culture is diminishing. Recently, several studies attempted to simultaneously utilize various sensors to record delicate and sophisticated performances of intangible cultural heritage (ICH). Although painting is one of the most common ICH of human history, few research studies have recorded traditional painting work. In this paper, we aim to lay the groundwork for reviving Korean painting, even if there would be no painters to produce these traditional Korean paintings in the future. We propose a novel multisensor-based acquisition system that records traditional Korean painting work while minimizing interference in the work. The proposed system captures real-time data originating from the painter, brushes, pigments, and canvas, which are the essential components of the painting work. We utilized the proposed system to capture the painting work by two experts, and we visualize the captured data. We showed the various results of statistical analysis, and also discussed the usability.

The effect of calcium (Ca2+) on the carbon dioxide (CO2) corrosion of mild steel was investigated in simulated saline aquifer environments (1 wt% sodium chloride [NaCl], 80°C, pH 6.6) with different concentrations of Ca2+ (10, 100, 1,000, and 10,000 ppm). Electrochemical methods (open-circuit potential [OCP]) and linear polarization resistance [LPR] measurements) were used to evaluate the corrosion behavior. Surface analysis techniques (scanning electron microscopy [SEM], energy-dispersive x-ray spectroscopy [EDS], and x-ray diffraction [XRD]) were used to characterize the morphology and identity the corrosion products. The results showed that with low concentrations of Ca2+ (10 ppm and 100 ppm), the corrosion rate decreased with time as a result of the formation of protective iron carbonate (FeCO3) and/or mixed carbonate (FexCayCO3) (x + y = 1). However, the presence of high concentrations of Ca2+ (1,000 ppm and 10,000 ppm) resulted in the change of corrosion product from protective FeCO3 to non-protective calcium carbonate (CaCO3), and an increasing corrosion rate with time. Results of surface analysis revealed a different steel surface morphology with pitting observed in the presence of 10,000 ppm Ca2+.

The objective of the present study is to evaluate the corrosion properties of pipeline steels in CO2/H2S/H2O mixtures with different amounts of water (undersaturated and saturated) related to a natural gas transportation pipeline. Corrosion behavior of carbon steel, 1Cr steel, and 3Cr steel was evaluated using an autoclave with different combinations of CO2 partial pressure and temperature (8 MPa/25°C and 12 MPa/80°C) with 200 ppm H2S. The corrosion rate of samples was determined by weight-loss measurements. The surface morphology and the composition of the corrosion product layers were analyzed using surface analytical techniques (scanning electron microscopy and energy dispersive x-ray spectroscopy). Results showed that the corrosion rate of materials in supercritical and liquid phase CO2 saturated with water was very low (<0.01 mm/y). However, adding 200 ppm of H2S to the supercritical and liquid CO2 system caused mild corrosion (<0.5 mm/y). Reducing water content to 100 ppm in the supercritical and liquid CO2 systems with 200 ppm of H2S reduced the corrosion rate to less than 0.01 mm/y.

The objective of the present study was to evaluate the effect of alloying elements (Cr, Mo, and Cu) on the corrosion behavior of low carbon steel in CO2 environments. Six samples were prepared with varying Cr content from 0 wt% to 2 wt% and with added 0.5 wt% of Mo and Cu; the specimens had ferritic/pearlitic microstructures. Steel samples were exposed to a CO2-saturated 1 wt% NaCl solution with different combinations of pH and temperature (pH 4.0 at 25°C, pH 6.6 at 80°C, and pH 5.9 at 70°C). Changes in corrosion rate with time were determined by linear polarization resistance measurements. The surface morphology and the composition of the corrosion product layers were analyzed by surface analysis techniques (scanning electron microscopy and energy dispersive x-ray spectroscopy). Results showed that the presence of Cr and Cu showed a slight positive effect on the corrosion resistance at pH 4.0 and 25°C. At pH 6.6 and 80°C, regardless of the alloying elements, the trend of corrosion rate with time was similar, i.e., the corrosion rate of all specimens decreased with time resulting from the formation of protective FeCO3. A beneficial effect of Cr presence was clearly seen at “gray zone” conditions: pH 5.9 and 70°C, where steel sample without Cr showed no decrease in corrosion rate with time. The presence of Cr in the steel promoted the formation of protective FeCO3 with Cr enrichment and it decreased the corrosion rate.

ObjectiveSwine manure in Korea is separated into solid and liquid phases which are composted separately and then applied on land. The nutrient accumulation in soil has been a big issue in Korea but the basic investigation about nutrient input on arable land has not been achieved in detail. Within the nutrient production from livestock at the national level, most values are calculated by multiplication of the number of animals with the excreta unit per animal. However, the actual amount of nutrients from swine manure may be totally different with the nutrients applied to soil since livestock breeding systems are not the same with each country.MethodsThis study investigated 15 farms producing solid compost and 14 farms producing liquid compost. Composting for solid phase used the Turning+Aeration (TA) or Turning (T) only methods, while liquid phase aeration composting was achieved by continuous (CA), intermittent (IA), or no aeration (NA). Three scenarios were constructed for investigating solid compost: i) farm investigation, ii) reference study, and iii) theoretical P changes (ΔP = 0), whereas an experiment for water evaporation was conducted for analyzing liquid compost.ResultsIn farm investigation, weight loss rates of 62% and 63% were obtained for TA and T, respectively, while evaporation rates for liquid compost were 8.75, 7.27, and 5.14 L/m2·d for CA, IA, and NA, respectively. Farm investigation provided with the combined nutrient load (solid+liquid) of VS, N, and P of 117.6, 7.2, and 2.7 kg/head·yr. Nutrient load calculated from farm investigation is about two times higher than the calculated with reference documents.ConclusionThe nutrient loading coefficients from one swine (solid+liquid) were (volatile solids, 0.79; nitrogen, 0.53; phosphorus, 0.71) with nutrient loss of 21%, 47%, and 29%, respectively. The nutrient count from livestock manure using the excretion unit has probably been overestimated without consideration of the nutrient loss.

The objective of the present study was to identify and quantify the key issues that affect the integrity of carbon steel in high-pressure CO2 and CO2/H2S environments and to establish potential corrosion mitigation strategies using low Cr alloy steels and corrosion inhibitors. The experiments were performed in a 7.5 L autoclave with two combinations of CO2 partial pressure and temperature (12 MPa/80°C and 8 MPa/25°C) with different H2S concentrations (0 ppm, 100 ppm, and 200 ppm). The corrosion behavior of specimens was evaluated using electrochemical measurements and surface analytical techniques. Results showed that the addition of corrosion inhibitor decreased corrosion rate significantly from 90 mm/y to below 0.1 mm/y at supercritical CO2 condition (12 MPa CO2, 80°C). However, insufficient protection was achieved from low Cr alloy steels. The addition of small amounts of H2S reduced the corrosion rate of carbon steel in high-pressure CO2 environments. However, the corrosion rate was still higher than the targeted rate (<0.1 mm/y). Additional protection was required in order to achieve the target. Utilizing 400 ppm of an imidazoline-type corrosion inhibitor reduced the corrosion rate of carbon steel below 0.1 mm/y in a high-pressure CO2 condition with H2S. Compared to carbon steel, the corrosion resistance of low Cr steels was lower in the corresponding CO2 conditions with H2S.

The objective of the present study was to evaluate the corrosion properties of carbon steel in supercritical carbon dioxide (CO2)/brine mixtures related to the deep water oil production development. Corrosion tests were performed in 25 wt% sodium chloride (NaCl) solution under different CO2 partial pressures (4, 8, 12 MPa) and temperatures (65°C, 90°C). Corrosion behavior of carbon steel was evaluated using electrochemical methods (linear polarization resistance [LPR] and electrochemical impedance spectroscopy [EIS]), weight-loss measurements, and surface analytical techniques (scanning electron microscopy [SEM], energy-dispersive x-ray spectroscopy [EDS], x-ray diffraction [XRD], and infinite focus microscopy [IFM]). The corrosion rates measured at 65°C showed a high corrosion rate (~10 mm/y) and a slight difference with pressure. Under these conditions, the sample surface was locally covered by iron carbide (Fe3C), which is porous and non-protective. However, the corrosion rates measured at 90°C increased with time at the initial period of the test and decreased to a very low value (~0.05 mm/y) due to the formation of protective iron carbonate (FeCO3) layer regardless the CO2 partial pressure.

A predictive model was developed for corrosion of carbon steel in carbon dioxide (CO2)-loaded aqueous methyldiethanolamine (MDEA) systems, based on modeling of thermodynamic equilibria and electrochemical reactions. The concentrations of aqueous carbonic and amine species (CO2, bicarbonate [HCO3−], carbonate [CO32−], MDEA, and protonated MDEA [MDEAH+]) as well as pH values in the MDEA solution were calculated. The water chemistry model showed a good agreement with experimental data for pH and CO2 loading, with an improved correlation upon use of activity coefficients. The electrochemical corrosion model was developed by modeling polarization curves based on the given species's concentrations. The required electrochemical parameters (e.g., exchange current densities, Tafel slopes, and reaction orders) for different reactions were determined from experiments conducted in glass cells. Iron oxidative dissolution, HCO3− reduction, and MDEAH+ reduction reactions were implemented to build a comprehensive model for corrosion of carbon steel in an MDEA-CO2-water (H2O) environment. The model is applicable to uniform corrosion when no protective films are present. A solid foundation is provided for corrosion model development for other amine-based CO2 capture processes.