Surface Observations Research Articles

Probabilistic estimation of rheological properties in subduction zones using sequences of earthquakes and aseismic slip

Abstract Constraining the effective rheology of major faults contributes to improving our understanding of the physics of plate boundary deformation. Geodetic observations over the earthquake cycle are often used to estimate key rheological parameters, assuming specific laboratory-informed classes of viscous or frictional rheological models. However, differentiating between various rheological model classes using only observations of a single earthquake (coseismic and postseismic deformation) is difficult—especially in the presence of coarse spatiotemporal sampling, inherent observational noise, and non-uniqueness of the inverted properties. In this study, we present a framework to estimate key rheological parameters of a subduction zone plate interface using simulations of sequences of earthquakes and aseismic slip, constrained by pre- and postseismic surface displacement timeseries. Our simplified forward model consists of a two-dimensional subduction zone, represented by a discretized planar fault or narrow shear zone, divided into a locked, shallow region (“asperity”) experiencing periodically imposed coseismic events, and a stress-driven creeping section governed by power-law viscoelasticity or rate-dependent friction. Our inverse model fits the rheological parameters of the interface to surface displacement timeseries in a Bayesian probabilistic way. We validate that our proposed framework can successfully recover depth-dependent profiles of effective viscosity using a synthetic dataset of pre- and postseismic observations. Our first set of numerical experiments show that our framework is only mildly sensitive to uncertainties in the rupture history or assumed coseismic slip, making it robust enough to be applied to real observations of subduction zones. Our second set of tests considers the similarities of surface displacement timeseries between synthetic models that model the plate interface either as a shear zone described by power-law viscosity, or a surface described by rate-dependent friction. Here, we find that the ability to fit surface observations using functional or mechanical models assuming frictional behavior does not constitute sufficient evidence to actually infer frictional behavior at depth, as the surface expressions are virtually indistinguishable from deformation generated from models with depth-variable power-law viscous behavior. Based on our numerical experiments, we conclude that studies that aim to infer the mechanical behavior and rheological properties at depth in subduction zones should consider the surface expression from time periods representative of the entire seismic cycle. Graphical Abstract

Regional Trends and Spatial Gradients of Total Column Methane over India, China, and USA─Implications for Emissions from Coal Mining and Oil/Gas Exploitation.

Observation-based verification of regional/national methane (CH4) emission trends is crucial for transparent monitoring and mitigation strategy planning. Although surface observations track the global and sub-hemispheric emission trends well, their sparse spatial coverage limits our ability to assess regional trends. Dense satellite observations complement surface observations, offering a valuable means to validate emission trends, especially in regions where emissions changes are substantial but debated. The uncertainty surrounding the rate of increase in fugitive coal mine emissions in China and emissions from unconventional oil and natural gas (ONG) exploration in the United States underscores the need for rigorous validation. Here, we examine the time evolution of total column dry-air mole fractions of CH4 (XCH4) during 2010-2020 by comparing observations from the GOSAT satellite with simulations from an atmospheric chemistry-transport model (ACTM). This study analyzes emissions and XCH4 trends in global totals and regions of India, China, the USA, and the global tropics. Our results suggest that GAINSv4 emission inventory overestimates the emission increase rate for the unconventional ONG sector of USA by about 3 times, while EDGARv6 inventory overestimates coal mine emissions in China. Emission increases in China and India agree with those estimated by GAINSv4. Analysis of spatially integrated XCH4 statistics (mean, 1-σ standard deviation) reveals a slight systematic underestimation of total emissions in China and bias (in both directions) in different parts of USA. Our results suggest that long-term satellite observations and ACTM simulations can effectively validate emission inventories for CH4 emissions and emission trends regionally.

Recycling of Disposable Face Mask: Experimental Studies on Different Types of Polymer Mixture

The COVID-19 pandemic has caused significant impacts on the environment since the use of disposable face masks leads to the accumulation of plastic waste. In this study, a two-step extrusion and injection molding was performed to manufacture polymer blends consisting of 80% used face mask and 20% fraction of one of these recycled polymer mixtures: polypropylene (PP), high-density polyethylene (HDPE), and PET. ASTM D256 standard was used to evaluate the mechanical properties of the resulting polymer blend materials, while the physical performance was assessed by analyzing the shrinkage. It was found that adding other polymeric mixtures could not enhance the mechanical properties of pure disposable face masks, as measured by the impact strength. However, incorporating the recycled polymer into the face mask mixture is revealed to decrease shrinkage. Observation of the morphology surface of the fracture impact specimen using a Scanning Electron Microscope (SEM) confirmed the less miscibility within the recycled polymer/face mask. The blend, which contains recycled PET, showed the lowest percentage of shrinkage. Taking advantage of its recyclability characteristic, this current work may provide an alternative approach for using the disposable face mask in low load-bearing applications.

Contributions of climatic factors and vegetation cover to the temporal shift in Asian dust events

Asia is one of the largest dust source regions in the world. However, the temporal variations and drivers of different types of dust events in this region remain unclear. Based on surface observation data, we explored spatiotemporal changes in three types of dust events and their driving factors in Asia by using machine learning methods. Results indicated that the frequency of moderate dust events (MDE) and severe dust events (SDE) decreased significantly from 2000 to 2022, which could be primarily attributed to a decrease in strong wind days (contribution >50%), and to a lesser extent to increases in soil moisture, precipitation, and leaf area index (LAI). When the daily maximum wind speed exceeds 13.0 m/s, the probability of MDE tends to decrease, while the probability of SDE tends to increase. These findings enhance our understanding of the variation in frequency and intensity of dust events in response to climate change.

Analyses of the Properties of the NiO-Doped Ga2O3 Wide-Bandgap Semiconductor Thin Films

The study began by pre-sintering Ga2O3 powder at 950 °C for 1 h, followed by the preparation of a mixture of Ga2O3 and 12 at% NiO powders to fabricate a source target material. An electron beam (e-beam) system was then used to deposit NiO-doped Ga2O3 thin films on Si substrates. X-ray diffraction (XRD) analyses revealed that the pre-sintered Ga2O3 at 950 °C exhibited β-phase characteristics, and the deposited NiO-doped Ga2O3 thin films exhibited an amorphous phase. After the deposition of the NiO-doped Ga2O3 thin films, they were divided into two portions. One portion underwent various analyses directly, while the other was annealed at 500 °C in air before being analyzed. Field-emission scanning electron microscopy (FESEM) was utilized to process the surface observation, and the cross-sectional observation was primarily used to measure the thickness of the NiO-doped Ga2O3 thin films. UV-Vis spectroscopy was used to calculate the bandgap by analyzing the transmission spectra, while the Agilent B1500A was employed to measure the I-V characteristics. Hall measurements were also performed to assess the mobility, carrier concentration, and resistivity of both NiO-doped Ga2O3 thin films. The first innovation is that the 500 °C-annealed NiO-doped Ga2O3 thin films exhibited a larger bandgap and better electrical conductivity. The manuscript provides an explanation for the observed increase in the bandgap. Another important innovation is that the 500 °C-annealed NiO-doped Ga2O3 thin films revealed a high-energy bandgap of 4.402 eV. The third innovation is that X-ray photoelectron spectroscopy (XPS) analyses of the Ga2p3/2, Ga2p1/2, Ga3d, Ni2p3/2, and O1s peaks were conducted to further investigate the reasons behind the enhanced electrical conductivity of the 500 °C-annealed NiO-doped Ga2O3 thin films.

Verification of Appearance Failure in Application of Injection Foam Molding to Automobile Exterior Parts by Short Shot Method ～The Process of Dimple Generation through Surface Observation～

Verification of Appearance Failure in Application of Injection Foam Molding to Automobile Exterior Parts by Short Shot Method ～The Process of Dimple Generation through Surface Observation～

Dynamics of Spatio-temporal Occupation of Biological Soils Crusts Using RS and GIS Approach in the Saria Catchment, West-central Region of Burkina Faso

In the semi-arid environments of sub-Saharan Africa, the combined action of climatic factors and human activities degrades the vegetation cover, resulting in soils that are vulnerable to the risk of erosion. This is when micro-organisms of various kinds, known as biological crusts, colonise the soil surface, playing a part in the pedogenetic processes and combating soil degradation. The aim of this study is to investigate the spatio-temporal occupation dynamics of biological crusts in the Saria catchment using remote sensing and geographic information systems. The methodology is based on a geomatics approach that integrates the use of Landsat-8 OLI/TIRS satellite images, geographic information systems and fieldwork. The processing of Landsat-8 OLI satellite images and the pedomorphological and environmental characterization of soils have made possible to map mainly two types of soils i.e. leached tropical ferruginous soils and low-humidity hydromorphic soils with surface pseudogley. After this step, the field work enabled us to identify the land cover units in our study area from which the in-situ observations of soils surfaces revealed that biological crusts are more developed on the soils of the fallow plots (30% - 95%) than the bare (5% - 15%) and field soils (5% - 10%). The results of this study showed that the level of development of soils biological crusts is linked to the plots disturbance and its ages. In conclusion the use of remote sensing and geographic information systems is an effective and less expensive technique for mapping soil types and land cover units covered by biological crusts.

Observation Angle Effect of Near-Ground Thermal Infrared Remote Sensing on the Temperature Results of Urban Land Surface

During the process of urbanization, a large number of impervious land surfaces are replacing the biologically active surface. Land surface temperature is a key factor reflecting the urban thermal environment and a crucial factor affecting city livability and resident comfort. Therefore, the accurate measurement of land surface temperature is of great significance. Thermal infrared remote sensing is widely applied to study the urban thermal environment due to its distinctive advantages of high sensitivity, wide coverage, high resolution, and continuous measurement. Low-altitude remote sensing, performed using thermal infrared sensors carried by unmanned aerial vehicles (UAVs), is a common method of land surface observation. However, thermal infrared sensors may experience varying degrees of sway due to wind, affecting the quality of the data. It is still uncertain as to what degree angle changes affect thermal infrared data in urban environments. To investigate this effect, a near-ground remote sensing experiment was conducted to observe three common urban land surfaces, namely, marble tiles, cement tiles and grasses, at observation angles of 15°, 30°, 45°, and 60° using a thermal infrared imager. This is accompanied by synchronous ground temperature measurements conducted by iButton digital thermometers. Our results suggest that the temperature differences between the remote sensing data of the land surface and the corresponding ground truth data increase as a function of the increasing observation angle of the three land surfaces. Furthermore, the differences are minor when the observation angle changes are not more than 15° and the changes are not the same for different land surfaces. Our findings increase the current understanding of the effects of different angles on thermal infrared remote sensing in urban land surface temperature monitoring.

The Effect of Surface Observations on Enhancing the GIIRS Thermodynamic Profile Retrieval

Understanding boundary-layer atmospheric temperature and moisture is essential for advancing our knowledge of the Earth system. This study adopts a one-dimensional variational (1DVAR)-based technique to integrate spaceborne measurement and ground-based observations for improving the retrieval of low-level atmospheric profiles. The performance of the algorithm under different atmospheric and observational scenarios, such as surface-air and skin temperature differences (∆T), surface pressure (Ps), and satellite zenith angle, respectively, has been systematically evaluated using the Geosynchronous Interferometric Infrared Sounder (GIIRS) on board the Fengyun-4A satellite as an example. Through theoretical information analysis, using both simulated and actual data experiments, this study demonstrates that incorporating ground-based temperature and moisture observations significantly enhances retrieval accuracy with 1DVAR, particularly over elevated terrain. The new algorithm is more effective in low-level temperature retrievals when air temperatures are colder relative to surface-skin temperatures, and it also shows greater benefit for water-vapor retrievals when the temperature difference between the air and the skin is minimal. However, as the zenith angle increases to 55°, the accuracy of temperature retrievals deteriorates, although this is mitigated by the combination of surface-air temperature observations. Notably, the positive impact of surface observations extends to approximately 100–200 hPa above the surface, underscoring the importance of accurate ground-based measurements in conjunction with spaceborne data for atmospheric profiling.

In Situ Operando Indicator of Dry Friction Squeal

In various applications, dry friction could induce vibrations. A well-known example is frictional braking systems in ground transportation vehicles involving a sliding contact between a rotating and a stationary part. In such scenarios, the emission of high-intensity noise, commonly known as squeal, can present human health risks based on the noise’s intensity, frequency, and occurrences. Despite the importance of squeal in the context of advancing urbanization, the parameters determining its occurrence remain uncertain due to the complexity of the involved phenomena. This study aims to identify a relevant operando indicator for predicting squeal occurrences. To this end, a pin-on-disc test rig was developed to replicate various contact conditions found in road profiles and investigate resulting squealing. Each test involves a multimodal instrumentation, complemented by surface observations. It is illustrated that the enhanced thermal indicator identified is relevant because it is sensitive to the thermomechanical and tribological phenomena involved in squealing.

The differences between remote sensing and in situ air pollutant measurements over the Canadian oil sands

Abstract. Ground-based remote sensing instruments have been widely used for atmospheric research, but applications for air quality monitoring remain limited. Compared to an in situ instrument that provides air quality conditions at the ground level, most remote sensing instruments (nadir viewing) are sensitive to a broad range of altitudes, often providing only integrated column observations. These column data can be more difficult to interpret and to relate to surface values and hence to “nose-height-level” health factors. This research utilized ground-based remote sensing and in situ air quality observations in Canada's Athabasca oil sands region to investigate some of their differences. Vertical column densities (VCDs) of SO2 and NO2 retrieved by Pandora spectrometers located at the Oski-Otin site at Fort McKay (Alberta, Canada) from 2013–2019 were analyzed along with measurements of SO2 and NO2 surface concentrations and meteorological data. Aerosol optical depth (AOD) observations by a CIMEL sunphotometer were compared with surface PM2.5 data. The Oski-Otin site is surrounded by several large bitumen mining operations within the Athabasca oil sands region with significant NO2 emissions from the mining fleet. Two major bitumen upgraders that are 20 km south-east of the site have total SO2 and NO2 emissions of about 40 and 20 kt yr−1, respectively. It was demonstrated that remote sensing data from Pandora and CIMEL combined with high-vertical-resolution wind profiles can provide information about pollution sources and plume characteristics. Elevated SO2 VCDs were clearly observed for times with south and south-eastern winds, particularly at 200–300 m altitude (above ground level). High NO2 VCD values were observed from other directions (e.g., north-west) with less prominent impacts from 200–300 m winds. In situ ground observations of SO2 and NO2 show a different sensitivity to wind profiles, indicating they are less sensitive to elevated plumes than remote sensing instruments. In addition to measured wind data and lidar-observed boundary layer height (BLH), modelled wind profiles and BLH from ECMWF Reanalysis v5 (ERA5) have been used to further examine the correlation between column and surface observations. The results show that the height of emission sources (e.g., emissions from high stacks or near the surface) will determine the ratio of measured column and surface concentration values (i.e., could show positive or negative correlation with BLH). This effect will have an impact on the comparison between column observations (e.g., from the satellite or ground-based remote sensing instruments) with surface in situ measurements. This study explores differences between remote sensing and in situ instruments in terms of their vertical, horizontal, and temporal sampling differences. Understanding and resolving these differences are critical for future analyses linking satellite, ground-based remote sensing and in situ observations in air quality monitoring and research.

HALOBATES: An Autonomous Surface Vehicle for High-Resolution Mapping of the Sea Surface Microlayer and Near-Surface Layer on Essential Climate Variables

Abstract Essential climate variables (ECVs) are physical, chemical, or biological parameters supporting the characterization of the climate system. The oceanic ECVs temperature and salinity have been defined for the sea surface (upper 1 mm) and bulk water (upper 2 m). Direct observation and sampling of the sea surface from ships and buoys are limited due to the potential loss of integrity of the sea surface and contamination by the research platform. The design, development, and operation of a research vehicle with autonomous capabilities based on commercially available components are described in this study. The autonomous operation and fully automated sampling enable high-resolution mapping of the sea surface microlayer (SML), i.e., the upper < 1-mm layer and the near-surface layer (<1.2 m). Sampling the SML is based on a rotating glass disk sampler. The autonomous surface vehicle HALOBATES has been equipped with multiple conductivity–temperature–depth (CTD) sensors in a flow-through system to measure both sea surface and bulk temperature and salinity. The performance of the autopilot under various scenarios is demonstrated. Typical anomalies of ECVs within the SML and near-surface layer are evident and forced by both atmospheric and oceanic processes. Data analyses reveal HALOBATES’ ability to resolve thermohaline structure on different spatial and temporal scales, for example, small-scale freshwater lenses and thermohaline changes across oceanic fronts. The integration of an acoustic Doppler current profiler supports the interpretation of thermohaline structures. HALOBATES is a platform with cutting-edge technology for understanding climate-related processes between the ocean and atmosphere and providing high-resolution sea surface data for validating satellite products of ECVs. Significance Statement An autonomous surface vehicle was developed to address the challenges in the in situ measurement of essential climate variables at the sea surface (upper 1 mm) and near-surface layer (upper 1 m) of the ocean. Autonomous operation for up to 12 h and fully automated sampling enable high-resolution mapping of the sea surface and near-surface layers. The ability of the vehicle to resolve thermohaline structures at various spatial and temporal scales is demonstrated, providing valuable data on freshwater fluxes (evaporation minus precipitation) between the ocean and the atmosphere. This cutting-edge technology enhances the understanding of climate-related processes, offering crucial “sea surface data” for validating satellite products of essential climate variables.

Compressive properties and microstructure of hybrid fiber-reinforced fly ash/slag-based geopolymers at elevated temperatures

This study investigates the effects of fly ash ceramsite (FACM) and hybrid fibers (with varying steel fiber contents) on the mass loss, compressive performance, crack development, and microstructure of hybrid fiber-reinforced fly ash/slag-based geopolymers (HFRG) at high temperatures. HFRG samples with different steel fiber volume fractions (0%, 0.5%, 1%, and 1.5%) were prepared and subjected to a controlled heating process (20°C, 200°C, 400°C, 600°C, and 800°C). Key properties, including mass loss, compressive strength, and crack patterns, were measured at elevated temperatures, with additional microstructural analysis conducted via SEM, XRD, and FTIR. Results showed that a 0.5% steel fiber content can suppress mass loss at high temperatures, while 1% steel fiber significantly enhances HFRG's compressive performance under heat. Compared to HFRG-0, HFRG-1.0 showed a 39% increase in peak stress, a 41% increase in strain, a 4.7% increase in elastic modulus, and a 108% increase in energy absorption capacity at 200°C. Surface observations revealed that crack area significantly decreased with increased steel fiber content. Microstructural analysis indicated that internal porosity increases, and thermal decomposition intensifies with rising temperature. This study provides key insights into the axial compression performance of HFRG for high-temperature applications and offers a detailed analysis of the effects of lightweight aggregates and hybrid fibers.

Growth of Highly Oriented Crystalline Silver Nanostructures on MgO (001) Substrates By Pulsed Laser Ablation and Application to SERS Substrates

Surface enhanced Raman scattering (SERS) substrates are expected to be applied to some functional devices such as high-sensitive biosensors and photocatalysts.[1-2] In order to produce metal nanostructures, electron beam lithography and chemical method have mainly been used so far. Although these methods are effective for nano-level microfabrication, there are problems such as the need for multiple processes, unsuitability for large-area processing, poor mass production, and susceptibility to surface oxidation. For clearing these problems, we have fabricated SERS substrates by depositing metal nanostructures on MgO(001) substrates using the pulsed laser ablation (PLA) method,[3] which is a one-step fabrication process. In previous research, we produced gold nanostructures by using PLA[4]. The wavelength of plasmon resonances due to the gold nanostructures exhibited in the infrared region, and therefore laser beam with 785 nm was utilized to SERS and Raman spectroscopy. We observed significant strong SERS signals after applying the gold nanostructures to SERS substrates. However, we also observed strong Raman signals due to the MgO(001) substrate, resulting in a spectrum where the SERS signals and the Raman signals interfering. To reduce the Raman signal due to the MgO(001) substrate, it is necessary to decrease a wavelength of an excitation laser which is equipped with the Raman system because the penetration depth of the laser beam into the MgO(001) substrate becomes shallower. Therefore, we focused on silver nanostructures because the wavelength of plasmon resonances was shorter than those of gold. The SERS substrates, which consists in silver nanostructures on MgO(001) substrate, expects to resonate with visible light. Consequently, the SERS signals will be generated to irradiate a laser beam with 532 nm, leading to reduce the Raman signals due to MgO(001) substrate. In this study, silver nanostructures with plasmon resonance wavelengths in the visible light region were fabricated by the PLA method. Silver nanostructures are deposited on a MgO(001) substrate (Furuuchi; size: 10×10mm2 and thickness: 0.5mm) by PLA. A Silver target (Furuuchi; diameter: 13mm, 99.99%) and MgO(001) substrate were located on a vacuumed chamber. The chamber was pumped down to 10-5 Torr and the substrate was treated by outgas (350℃, 30min) and cleaning (800℃, 30min) using a silicon-carbide heating system. After cleaning, the deposition temperature was set to 350 ℃, 450 ℃ and 550 ℃. Argon or oxygen gas was flowed in the vacuum chamber. A pulsed laser beam (LOTIS TII, LS-2147: wavelength: 355 nm, pulse width: 10 ns, laser fluence: 0.8 J/cm2, repetition frequency: 4 Hz, and number of laser pulses: 7000) was irradiated through a laser insertion window into the installed silver target. Silver nanostructures were fabricated by ablation plumes and depositing them on a MgO(001) substrate. Optical transmittance measurements of the silver nanostructures fabricated by the PLA method showed that they have an optical absorption peak in the visible light region around 600 nm. Surface observation by using an atomic force microscopy (AFM: Hitachi High-Tech, SPA 300, dynamic force mode) showed self-grown nanoparticles with edges and silver nanostructures was observed Ag (200) by a high angle x-ray diffraction (XRD: Rigaku, RINT2000). SERS measurements were carried out using 4-MBA, and a SERS substrate with an enhancement factor of 5.51×105 was successfully developed.

Al Electroplating on Etched CFRP Surfaces in AlCl3-EmImCl Ionic Liquids

Carbon fiber-reinforced plastics (CFRP) are composite materials of carbon fibers and resin. Since it is low in density, high in strength, and high in rigidity, it is used in many applications such as sports fields and automobiles. However, its surface wear resistance is not enough, and it is limited to using it as a material for friction. To improve wear resistance, CFRP surface modification by Al electroplating and surface anodizing were used in this study. Electroplating is one of the low-cost Al plating methods with easy control of plating film thickness. Since the surface consists of highly conductive carbon fibers and low conductive resin, only the carbon fibers are electroplated. In this study, to increase the occupancy of carbon fibers on the surface, the resin in CFRP was dissolved and removed by acid treatment. Then, Al electrodeposition experiments in ionic liquids were also conducted for the surface.CFRP (PEEK resin) was cut into 2 cm x 5 cm pieces and used as substrates. Surface etching treatments were performed under 5 molL-1 sulfuric acid at 373 K for 10 to 120 seconds. The ionic liquid used in the electrodeposition experiments was a mixture of 1-ethyl-3-methylimidazolium chloride (EmImCl) and AlCl3 at a molar ratio of 1: 2. As an additive, 1,10-phenanthroline was added to the ionic liquid to a concentration of 20 mmolL-1. In the Al electrodeposition experiments, a CFRP plate (before and after surface etching) was used as the working electrode; Al mesh and Al wire were used as the counter and reference electrodes, respectively. For electroplating, the condition was current pulse electrolysis at 20 mA cm-2, duty ratio 0.83, and temperature at 333 K. In the electroplating, applied electric charge corresponds to a targeted theoretical film thickness of 20 µm. The surface morphology of the electrodeposit before and after electrodeposition was observed by Scanning Electron Microscopy (SEM). Surface roughness was also measured using Confocal Laser Scanning Microscopy (LSCM).In surface observation after the etching of CFRP in 5 molL-1 sulfuric acid at 373 K, the surface became rougher as the etching time was increased. The surface roughness showed little change when the etching time was 60 and 120 s. The Al electrodeposits on the untreated CFRP surface were smooth with a roughness of 0.43 μm. Al deposits on the surface after etching treatment were 2.25 μm for 60 s treatment and 2.27 μm for 120 s treatment. From the SEM observation of the Al electrodeposits, the electrodeposits were formed along the carbon fibers. In addition, some parts with large gaps between carbon fibers were not covered by Al electrodeposits. It was considered this was due to the difficulty of electrolytes with high viscosity to penetrate into the gap.

Maintaining High Efficiency of Photoelectrochemical Gas-Phase CO2 Reduction Reaction for 500 h By Supplying Water Vapor to Cathode Surface

To supply more CO2 to a cathode, we have been studying a gas-phase CO2 reduction reaction (GCRR) cell, in which gas-phase CO2 is supplied and consumed in a reduction reaction with a metal fiber electrode (cathode) on a proton exchange membrane.1 We have reported that the faradaic efficiency of the CO2 reduction reaction (FE CO2RR)can be improved by changing the cathode materials (Au, Cu, etc.) in the GCRR cell.2 However, we also observed that the FE CO2RR decreases over time due to carbonate accumulation on the cathode surface, which is assumed to reduce the amount of gas-phase CO₂ supplied to the cathode surface. We considered that by removing the carbonate, we could maintain the FE CO2RR. In this study, we attempted to supply water vapor to the cathode surface. In addition, we theoretically derived the humidity conditions necessary for carbonate dissolution and experimentally verified whether the water vapor supply could remove generated carbonate and maintain the FE CO2RR during 500-h continuous tests, in a world first in GCRR cell research.We hypothesized that the carbonate dissolution rate surpassing the carbonate generation rate is essential for effective carbonate dissolution. To verify this hypothesis, we prepared two humidity conditions: a high-humidity condition with a higher dissolution rate and a low-humidity condition with a higher generation rate. The high-humidity condition was achieved using the bubbling method, resulting in CO2 humidities of 0.28 g/m3 and 0.024 g/m3 under high-humidity and low-humidity conditions, respectively. The CO2 flow rate was maintained at 35 sccm. The sample was prepared by thermocompression bonding an Au fiber sheet (area: 1 x 1 cm) and a proton exchange membrane Nafion 117 (manufactured by Sigma-Aldrich) at 423 K and 3.5 MPa, then positioned between the photoanode and the cathode chamber. An AlGaN/n-GaN heterostructure grown on a sapphire substrate served as the photoanode, with AlGaN serving as the light absorption layer. A NiO thin film was fabricated on the surface of AlGaN as a co-catalyst.3 The photoanode chamber was filled with a 1.0 mol/L KOH electrolyte solution, and the photoanode was immersed in the solution. The photoanode was irradiated with light from an Xe lamp with an irradiance of 2.2 mW/cm2 (λ ≤ 365 nm). To avoid the drop in photocurrent due to deterioration of the photoanode, the photoanode was replaced after 268 h and 308 h under high-humidity and low-humidity conditions, respectively. The photocurrent between the photoanode and cathode was measured using a potentiostat with an applied potential of 0.5 V, and the amount of product gases (H2, CO, CH4, C2H4) in the cathode chamber was measured with a gas chromatograph.Figure 1 shows the amount of CO and H2 production over irradiation time alongside images of the cathode surface after 500 h, under high-humidity and low-humidity conditions. The average photocurrent density over 500 h was 0.15 mA/cm2 under both high-humidity and low-humidity conditions. Photocurrent density is defined as photocurrent normalized by the area of the photoanode. This result suggests nearly identical average resistances of the reaction cells. Observation of the cathode surface after 500 h revealed minimal carbonate formation under high-humidity conditions (Fig. 1 (a)). On the other hand, under low-humidity conditions, the cathode surface was predominantly covered with carbonate (Fig. 1 (b)). Only CO and H2 gases were detected from the cathode chamber, with no other gases detected. The cumulative CO amounts produced after 500 h per photoanode area under high-humidity and low-humidity conditions were 1330 μmol/cm2 and 970 μmol/cm2, respectively (Fig. 1). In addition, the FE CO2RR calculated from the CO amount produced was 94% and 71%, respectively, and the FE CO2RR was maintained over 500 h under high-humidity conditions compared with low-humidity conditions. These results suggest that under high-humidity conditions, where the carbonate dissolution rate exceeded the generation rate, carbonate dissolution and removal occurred as hypothesized. Additionally, we considered that the removal of the carbonate resulted in the sustained CO2 supplied to the cathode surface.[1] S. Sato et al., The 89th ECSJ Spring Meeting, 1B14 (2022) (in Japanese).[2] S. Sato et al., The 90th ECSJ Spring Meeting,1C19 (2023) (in Japanese).[3] Y. Uzumaki et al., PRiME 2020, L04-3054 (2020). Figure 1

Observation of Leveler and Accelerator Behaviors in Copper Electroplating Using a Microfluidic Device

The high performance of modern integrated circuits is now owing to packaging technologies. Particularly, 3d-packaging using TSVs (Through Silicon Vias) has attracted large attention and entered use in high-end products. To fill conductor in TSVs, copper electroplating is used since extreme bottom-up is available using a combination of additives. Among additives, levelers have an important role, and extreme bottom-up can be seen with single addition of leveler without other additives. But in industry, still combination of leveler, suppressor and accelerator is commonly used. Then, we started to observe interaction of additives using the microfluidic device. In our previous study, interaction between the leveler and suppressors was studied and the leveler showed stronger adsorption compared to suppressors. In this study, mainly interaction between the leveler and the accelerator was mainly studied.Figure 1 showed a schematic of the experimental setup. Plating solutions containing different additives can be supplied sequentially and in-situ observation of a plating surface through an optical microscope is available. We performed chronoamperometries with sequential supply from the leveler to the accelerator, vice versa, and simultaneous supply. In the sequential supply experiments, it was found that the accelerator can adsorb on the leveler coated surface, and the leveler can also adsorb on the accelerator coated surface. Competitive adsorption between the leveler and the accelerator was suggested. Result with the simultaneous supply of the leveler and the accelerator is shown in figure 2. Initially, the current density with simultaneous addition was larger than the current density obtained with only leveler addition, which we expected. But after that, interestingly, current density with the simultaneous addition maintained lower than the case with only leveler addition. Further study will be needed to understand the phenomenon.

CO2 variability over a tropical coastal station in India: Synergy of observation and model

Carbon dioxide (CO2), being the prime greenhouse gas, has largest contribution in radiative forcing and global warming due to increased anthropogenic emissions leading to regional and global climate change. We performed CO2 measurements using a continuous monitoring instrument at a tropical coastal station at the southern tip of India (Thumba; 8.54° N, 76.86° E) during 2017–2021. Combining measurements with model simulations and satellite observations, present study aims to understand CO2 variabilities, contribution of various sources and role of dynamics. The observed trend of 2.19 ppm y−1 is well simulated (2.47 ppm y−1) by the chemistry-transport model (MIROC4-ACTM), which is contributed by trends in fossil fuel (4.59 ppm y−1), biosphere (−1.46 ppm y−1) and ocean (−0.66 ppm y−1) tracers of CO2 flux. Mean seasonal cycle with amplitude of about 8 ppm is observed, with a maximum during premonsoon (April) and minimum at the end of the monsoon season (September). The model reproduced the observed seasonal cycle well (r2 = 0.89) and showed that the seasonal peak is predominantly contributed by the land biospheric flux seasonality. Biospheric sink during postmonsoon is counterbalanced by emissions from fossil fuel burning. Biosphere and fossil fuel are major contributors in shaping the observed seasonal pattern with negligible seasonality in oceanic tracer due to its uniform flux patterns in the Indian Ocean. Mean diurnal pattern of CO2 exhibits lower values during daytime (cleaner marine airmass) and higher values during nighttime (continental airmass) with deeper diurnal amplitude in the winter (~50 ppm) than in the summer (~31 ppm). Seasonal pattern in total column CO2 from OCO-2 (Orbiting Carbon Observatory-2) is similar to the surface observations but shows nearly half of the observed seasonal amplitude. Long-term continuous measurements over distinct environments are desirable for further deepening the understanding of CO2 variability, estimation of regional carbon budget and for climate mitigation policies.

On the Multiscale Processes Leading to an Extreme Gust Wind Event in East China: Insights From Radar Wind Profiler Mesonet Observations

AbstractIn this study, a record‐breaking surface gust wind event of over 45 m s−1, which occurred in the coastal region of East China during the early evening hours of 30 April 2021, is examined. The dynamical characteristics of this event is explored by using a high‐resolution mesonet comprised of eight radar wind profilers (RWPs), surface observations, radar and satellite data. Observational analyses show the development of several cloud clusters ahead of the axis of a midlevel trough with pronounced baroclinicity, and the subsequent organization into a comma‐shaped squall system with a leading convective line over land and a trailing stratiform region moved offshore. The latter is embedded by a mesovortex with intense northerly rear inflows descending to the surface, accounting for the generation of the gusty winds. Results indicate the different roles of multi‐scale processes in accelerating the surface winds to extreme intensity. Specifically, the large‐scale baroclinic trough provides intense background rear inflows that are enhanced by the formation of the mesovortex, while moist downdrafts in the rear inflows account for the downward transport of horizontal momentum, leading to the generation of intense cold outflows and gusty winds close to the leading convective line. Despite the lack of sufficient observations for quantitative analysis, this study provides a qualitative analysis that offers valuable insights into the dynamics of extreme gusty winds. Moreover, the above results underscore the value of RWP mesonet observations in enhancing our understanding of extreme wind events and in improving the nowcasting and prediction efforts in the future.

Trans-1,4-poly(isoprene-co-butadiene) rubber enhances abrasion resistance in natural rubber and polybutadiene composites

This study investigates the integration of Trans-1,4-poly (isoprene-co-butadiene) rubber (TBIR) with natural rubber (NR) and cis-1,4-polybutadiene rubber (BR) to enhance the abrasion resistance of rubber composites. The NR/BR blend, a significant material in the rubber industry, is limited by poor interfacial compatibility and non-uniform filler distribution, resulting in heightened abrasion and failure. The addition of TBIR, along with carbon black (CB) and graphene oxide (GO), aims to achieve synergistic reinforcement. The results show that with 20 phr TBIR, the DIN abrasion of the composites decreased by 13.8 %, meeting the ISO 10247 standard for high-abrasion conveyor belt cover rubber. The improvement in wear resistance is attributed to TBIR's crystalline nature, which enhances tear strength, hardness, and elongation at break. TBIR also acts as an interface compatibility agent, improving the network structure of the rubber and fillers, thus enhancing composite performance. Observations of Schallamach waves, abrasion surface, and debris morphology indicate that the primary surface abrasion mechanism for the NR/BR/TBIR composites is abrasive abrasion. Regression analysis reveals that the abrasion resistance of the NR/BR/TBIR composites correlates with their mechanical properties and thermal conductivity, with higher tear strength, hardness, and elongation at break correlating with reduced surface damage due to abrasive abrasion. This research provides valuable insights into the development of high-abrasion-resistant natural rubber composites and the investigation of abrasion resistance mechanisms in rubber composites.