Surface Observations Research Articles

THE DITCH OF THE 17th CENTURY FOR MOORING BOATS IN THE VOZNESENSKYI MONASTERY NEAR DUBNO: CONSTRUCTION AND MATERIALS

Archaeological research carried out on Dubovets Island in 2022 made it possible to discover and study part of the ditch for mooring boats. The rich collection of materials with a wide range of categories was obtained from the ditches fill due to the fact that it accumulated the garbage and kitchen waste. At a certain point in time, a lot of fish were scaled near it which resulted in a continuous layer of scales. Judging by surface observations, this ditch stretched from the edge of the floodplain, i.e. the former pond bank, to the place where monastery-related objects were concentrated on the top of the hill, some of which were uncovered by excavations. Position and structure of the ditch indicate that it was used as a canal for launching and mooring of boats, which was a quite appropriate engineering solution in the conditions of a changing water levels in the pond and coastal reeds. The regular rows of stakes are the remains of protective wooden structures that strengthened the sandy sides of the ditch, apparently by weaving thin wood between them. The mixed sediments of layer 6 are traces of their destruction during the operation of the ditch. The analysis of archaeological materials from the ditch fill layers indicates that it was used during the 17th and 18th centuries. Object 83 is an important addition to the spatial and planning reconstruction of the monastery territory. It also serves as an example of an archaeological study of a peculiar technical structure that is not often discovered. Obviously, such ditches were built for residential complexes in the past where there was a need and the opportunity to attract the necessary labor. Ostriv Dubovets, as evidenced by the plans of the 17th and 18th centuries, was located near one of the riverbeds of the Ikva, which was more clearly visible during the period of low water in the pond. During the flood season, especially in spring, the valley between the island and the town was completely flooded. Thus, the water level near the island was not constant throughout the year, which made it impossible to arrange a simple berth. In addition, Ostriv Dubovets had a very gentle and elongated coastline, which was flooded for different lengths throughout the year. Therefore, for the convenience of embarkation and debarkation people, as well as loading and unloading boats on a dry section of the island’s shore, the construction of the discovered ditch was a necessary and original solution.

Arthroscopic reduction and internal fixation for fracture of the posterior process of the talus (Shepherd’s fracture): a case report

IntroductionFracture of the lateral tubercle of the posterior process of the talus (Shepherd fracture) is an uncommon injury seen in sport. It is secondary either to indirect trauma on the plantarflexed foot or to high-impact direct trauma. The fracture can be missed with conventional X-rays and therefore advanced imaging methods such as CT scans are usually warranted for management planning. There is a low threshold towards surgical management in the displaced or comminuted case as the delayed functional outcome with conservative treatment is frequently sub-optimal with long-term pain, degenerative changes and non-union. In this regard, recent years saw an increasing interest in the role of minimally invasive approaches for Shepherd´s fracture treatment, such as arthroscopic reduction and internal fixation (ARIF).Case reportWe present a case of a 27-year-old white male professional football player from Serbia who had Shepard fracture and successfully managed with arthroscopic osteosynthesis. The technical approach is detailed with posterior ankle arthroscopy offering the advantages of a minimally invasive approach with low morbidity and a rapid return to regular sporting activities.ConclusionThe utilization of the 2-port arthroscopic approach this method enables the direct observation of the articular surface along with the corresponding fracture lines, thereby affording the surgeon the chance to achieve accurate reduction via a minimally invasive soft tissue aperture. We advocate that Arthroscopic reduction and internal fixation (ARIF) is a reliable method for the fixation of Shepherd's fracture in the hands of experienced ankle arthroscopists.

Creep damage evolution by cavity nucleation and growth considering the cavity closure under cyclic loading conditions

AbstractCreep damage assessment is crucial for ensuring the long‐term reliability of key components operating at high temperatures. However, the existing studies on creep damage are mainly focused on constant loading conditions, while the effect of cyclic loading, which is a common loading mode in practice, remains unclear. In this paper, a series of stress‐controlled cyclic creep tests on the Inconel 718 superalloy were performed to investigate the influence of cyclic loading on creep damage evolution. The ex‐situ microstructural analyses, including fracture surface observations and EBSD measurements, were conducted to reveal the damage mechanisms under cyclic creep conditions. Furthermore, a cavity nucleation and growth model that accounts for the additional cavity closure was developed for the healing effect of cyclic creep damage evolution. The prediction results were consistent with the experimental data of cavity nucleation life and experimental life within a factor of 2.

Experimental investigation of abrasive potential and drilling efficiency at elevated temperatures via Cerchar rock scratching

To see if and how abrasive potential as well as drilling efficiency change due to rock heating, Cerchar scratch tests were performed on six types of rock at eight temperature levels. Results indicate that rock abrasivity is temperature-dependent. The change of rock abrasivity expressed by the Cerchar abrasivity index can be divided into two stages on either side of 500 °C. Meanwhile, the drilling efficiency expressed by the Cerchar abrasion ratio can significantly be enhanced, especially when the heating temperature exceeds 500 °C. The observation of damaged surfaces indicates that the material volume removed from the rock surface increase after rock heating. The worn steel surfaces (115CrV3 tool steel) shows the severe plastic deformation and fracturing associated with cracking, delamination, dislocation and chipping of the steel.

Improving biological and mechanical properties of bioprinted PCL-alginate-chondrocyte scaffolds for patellofemoral cartilage tissue regeneration

In this study, polycaprolactone (PCL) scaffolds have been employed as structural framework scaffolds for patellofemoral cartilage tissue regeneration. The biomechanical and biological properties of different scaffolds were investigated by varying alginate concentrations and the number of scaffold layers. Patellofemoral cartilage defects result in knee pain and reduced mobility, and they are usually treated with conventional methods, often with limited success. Generally, tissue-engineered PCL-alginate scaffolds fabricated by bioprinting technology show promise for enhanced cartilage regeneration due to the biocompatibility and mechanical stability of PCL. In addition, alginate is known for its cell encapsulation capabilities and for promoting cell viability. Biological and morphological assessments, utilizing water contact angle, cell adhesion tests, MTT assays, and scanning electron microscopy (SEM), informed the selection of the optimized scaffold. Comparative analyses between the initial optimal scaffolds with the same chemical composition also included flexural and compression tests and fracture surface observations using SEM. The controlled integration of PCL and alginate offers a hybrid approach, that assembles the mechanical strength of PCL and the bioactive properties of alginate for tissue reconstruction potential. This study aims to identify the most effective scaffold composition for patellofemoral articular cartilage tissue engineering, emphasizing cell viability, structural morphology, and mechanical integrity. The results showed that the optimum biomechanical and biological properties of scaffolds were obtained with a 10% alginate concentration in the monolayer of PCL structure. The findings contribute to regenerative medicine by advancing the understanding of functional tissue constructs, bringing us closer to addressing articular cartilage defects and related clinical challenges.

Experimental study on the effect of reaming on the fatigue life of split-sleeve cold-expanded Ti–6Al–4V alloy components

The split-sleeve cold expansion technique has been widely used in the aerospace industry to improve the fatigue life of metal components with holes. Due to the morphology change after the expansion, a reaming process is necessary to improve the machining accuracy of the hole surface. This final reaming process might change the residual stress distribution around the hole significantly but the effect of the reaming ratio has not been fully explored. This paper investigated the effect of reaming depth on the fatigue life of split-sleeve cold-expanded Ti–6Al–4V alloy components using a series of experiments, including the residual stress measurements, uniaxial fatigue tests, and fracture morphology observations. The expectations of the fatigue cycles were estimated using the 2-parameter Weibull distribution and the S-N curves of different components were acquired. Residual stress measuring results and the fracture surface observations explained the effect of cold expansion and reaming on the components. The experimental results showed that the fatigue life of the components decreased with the increase of the reaming ratio, demonstrating that excessive reaming depth is harmful to the fatigue performance of the cold-expanded components.

Effect of direct-quenching and tempering on hydrogen-induced delayed fracture resistance of high-strength bolt steel

This investigation attempts to explore the potential significance of controlled forging, i.e., direct-quenching at two different finish-forging temperatures of ∼930 °C (B8H sample) and ∼780 °C (B8L sample), and tempering at 600 °C in improving the hydrogen-induced delayed fracture (HIDF) resistance of a 1300-MPa-grade high-strength bolt steel by constant load tensile testing using circumferentially notched round bar specimens and hydrogen thermal analysis. The microstructural characteristics of the tested samples were analyzed and their influences on HIDF were discussed. The results showed that the B8L sample demonstrated a considerably increased HIDF resistance expressed by critical notch delayed fracture stress of 1825 MPa and a decreased hydrogen embrittled index of as low as 21% compared with those of 1675 MPa and 27% for the B8H sample, although the former exhibited slightly higher strength and absorbed hydrogen content. Scanning electron microscopy observation of the fracture surface demonstrated that the B8L sample prevented the brittle intergranular fracture with smaller quasi-cleavage facet and decreased area fraction of the brittle crack initiation zone compared with the B8H sample. The increased resistance to HIDF of the B8L sample is primarily because of its fine microstructure with increased number of finely distributed V-rich nanoscale MC precipitates and decreased dislocation density. It is proposed that controlled forging coupled with V-microalloying is a feasible and economical way to further increase the HIDF resistance of high-strength bolt steel.

Changes in South American surface ozone trends: exploring the influences of precursors and extreme events

Abstract. In this study, trends of 21st-century ground-level ozone and ozone precursors were examined across South America, a less-studied region where trend estimates have rarely been comprehensively addressed. Therefore, we provided an updated regional analysis based on validated surface observations. We tested the hypothesis that the recent increasing ozone trends, mostly in urban environments, resulted from intense wildfires driven by extreme meteorological events impacting cities where preexisting volatile organic compound (VOC)-limited regimes dominate. We applied the quantile regression method based on monthly anomalies to estimate trends, quantify their uncertainties and detect trend change points. Additionally, the maximum daily 8 h average (MDA8) and peak-season metrics were used to assess short- and long-term exposure levels, respectively, for the present day (2017–2021). Our results showed lower levels in tropical cities (Bogotá and Quito), varying between 39 and 43 nmol mol−1 for short-term exposure and between 26 and 27 nmol mol−1 for long-term exposure. In contrast, ozone mixing ratios were higher in extratropical cities (Santiago and São Paulo), with a short-term exposure level of 61 nmol mol−1 and long-term exposure levels varying between 40 and 41 nmol mol−1. Santiago (since 2017) and São Paulo (since 2008) exhibited positive trends of 0.6 and 0.3 nmol mol−1 yr−1, respectively, with very high certainty. We attributed these upward trends, or no evidence of variation, such as in Bogotá and Quito, to a well-established VOC-limited regime. However, we attributed the greater increase in the extreme percentile trends (≥ 90th) to heat waves and, in the case of southwestern South America, to wildfires associated with extreme meteorological events.

Atomic-Level Observation of Potential-Dependent Variations at the Surface of an Oxide Catalyst during Oxygen Evolution Reaction.

Understanding the intricate details of the surface atomic structure and composition of catalysts during the oxygen evolution reaction (OER) is crucial for developing catalysts with high stability in water electrolyzers. While many notable studies highlight surface amorphization and reconstruction, systematic analytical tracing of the catalyst surface as a function of overpotential remains elusive. Heteroepitaxial (001) films of chemically stable and lattice-oxygen-inactive LaCoO3 are thus utilized as a model catalyst to demonstrate a series of atomic-resolution observations of the film surface at different anodic potentials. The first key finding is that atoms at the surface are fairly dynamic even at lower overpotentials. Angstrom-scale atomic displacements within the perovskite framework are identified below a certain potential level. Another noteworthy feature is that amorphization (or paracrystallization) with no long-range order is finally induced at higher overpotentials. In particular, surface analyses consistently support that the oxidation of lattice oxygen is coupled with amorphous phase formation at the high potentials. Theoretical calculations also reveal an upward shift of oxygen 2p states toward the Fermi level, indicating enhanced lattice oxygen activation when atom displacement occurs more extensively. This study emphasizes that the degradation behavior of OER catalysts can distinctively vary depending on the overpotential level.

Aggravated surface O3 pollution primarily driven by meteorological variations in China during the 2020 COVID-19 pandemic lockdown period

Abstract. Due to the lockdown during the COVID-19 pandemic in China from late January to early April in 2020, a significant reduction in primary air pollutants, as compared to the same time period in 2019, has been identified by satellite and ground observations. However, this reduction is in contrast with the increase of surface ozone (O3) concentration in many parts of China during the same period from 2019 to 2020. The reasons for this contrast are studied here from two perspectives: emission changes and inter-annual meteorological variations. Based on top-down constraints of nitrogen oxide (NOx) emissions from TROPOMI measurements and GEOS-Chem model simulations, our analysis reveals that NOx and volatile organic compound (VOC) emission reductions as well as meteorological variations lead to 8 %, −3 % and 1 % changes in O3 over North China, respectively. In South China, however, we find that meteorological variations cause ∼ 30 % increases in O3, which is much larger than −1 % and 2 % changes due to VOC and NOx emission reductions, respectively, and the overall O3 increase in the simulations is consistent with the surface observations. The higher temperature associated with the increase in solar radiation and the decreased relative humidity are the main reasons that led to the surface O3 increase in South China. Collectively, inter-annual meteorological variations had a larger impact than emission reductions on the aggravated surface O3 pollution in China during the lockdown period of the COVID-19 pandemic.

Study of the Effects on the Strengthening Mechanism and Wear Behavior of Wear-Resistant Steel of Temperature Controlling in Heat Treatment.

To improve the wear resistance of the materials used for blades in engineering machinery, this study focused on the microstructural characteristics, mechanical properties, and wear behavior of HB500 grade wear-resistant steel developed using an optimized heat treatment system. To improve the temperature uniformity of the heat treatment furnace, the method of cyclic heating was used to heat the components. Carefully designing the quenching equipment, such as using a cross-shaped press, was employed to enhance the quenching effect and reduce the deformation of the steel plates. The crystal orientation analysis revealed a uniform and fine-grained microstructure, primarily characterized by plate-type tempered martensite, which indicated a good hardenability. The microstructure observations showed that the width of martensite is approximately 200 nm, with a significant presence of dislocations and carbides. Tensile tests and multi-temperature gradient impact tests indicated superior mechanical properties compared to similar grade wear-resistant steels, including a Rockwell hardness of 53, tensile strength of 1610 MPa, yield strength of 1404 MPa, and total elongation around 12.7%. The results of friction and wear experiments indicate that the wear rate decreases as the load increases from 100 N to 300 N, demonstrating an excellent wear resistance under a large load. Observations of the worn surfaces indicated that the wear mainly involved adhesive wear, fatigue wear, and oxidative wear. The properties' improvements were attributed to microstructure refinement and precipitation strengthening. This study indicates that designing a heat treatment system to control temperature uniformity and stability is feasible.

Refining tomography with generative neural networks trained from geodynamics

SUMMARY Inverse problems occur in many fields of geophysics, wherein surface observations are used to infer the internal structure of the Earth. Given the non-linearity and non-uniqueness inherent in these problems, a standard strategy is to incorporate a priori information regarding the unknown model. Sometimes a solution is obtained by imposing that the inverted model remains close to a reference model and with smooth lateral variations (e.g. a correlation length or a minimal wavelength are imposed). This approach forbids the presence of strong gradients or discontinuities in the recovered model. Admittedly, discontinuities, such as interfaces between layers, or shapes of geological provinces or of geological objects such as slabs can be a priori imposed or even suggested by the data themselves. This is however limited to a small set of possible constraints. For example, it would be very challenging and computationally expensive to perform a tomographic inversion where the subducting slabs would have possible top discontinuities with unknown shapes. The problem seems formidable because one cannot even imagine how to sample the prior space: is each specific slab continuous or broken into different portions having their own interfaces? No continuous set of parameters seems to describe all the possible interfaces that we could consider. To circumvent these questions, we propose to train a Generative Adversarial neural Network (GAN) to generate models from a geologically plausible prior distribution obtained from geodynamic simulations. In a Bayesian framework, a Markov chain Monte Carlo algorithm is used to sample the low-dimensional model space depicting the ensemble of potential geological models. This enables the integration of intricate a priori information, parametrized within a low-dimensional model space conducive to efficient sampling. The application of this approach is demonstrated in the context of a downscaling problem, where the objective is to infer small-scale geological structures from a smooth seismic tomographic image.

Application of the NCAR FastEddy® Microscale Model to a Lake Breeze Front

This study investigates how urban environments influence boundary layer processes during the passage of a Great Salt Lake breeze using a multi-scale modeling system, NCAR’s WRF-Coupled GPU-accelerated FastEddy® (FE) model. Motivated by the need for sub-10 m scale decision support tools for uncrewed aerial systems (UAS), the FE model was used to simulate turbulent flows around urban structures at 5 m horizontal resolution with a 9 km × 9 km domain centered on the Salt Lake City International Airport. FE was one-way nested within a 1 km resolution Weather Research and Forecasting (WRF) domain spanning 400 × 400 km. Focused on the late morning lake breeze on 3 June 2022, an FE simulation was compared with WRF outputs and validated using surface and radar observations. The FE simulation revealed low sensible heat flux and cool near-surface temperatures, attributed to a relatively low specification of thermal roughness suitable for previously tested FE applications. Lake breeze characteristics were minimally affected, as FE effectively resolved interactions between the lake breeze and urban-induced turbulent eddies, providing insights into fine-scale boundary layer processes. FE’s GPU acceleration ensured efficient simulations, underscoring its potential for aiding decision support in UAS operations in complex urban environments.

Odd Wilson surfaces

Previously, Wilson surface observables were interpreted as a class of Poisson sigma models. We profit from this construction to define and study the super version of Wilson surfaces. We provide some ‘proof of concept’ examples to illustrate modifications resulting from appearance of odd degrees of freedom in the target.

How we know Antarctica is rapidly losing more ice

ABSTRACT Satellite observations of the Antarctic surface since the 1990s, coupled with geophysical surveys of the flow and form of its giant ice sheet, have revealed accelerating loss of ice to the oceans. This, coupled with a reduction in floating sea ice surrounding the continent and the occurrence of unprecedented heatwaves, point to a continent being changed irreversibly by fossil-fuel burning and the global heating that results. A changing Antarctic continent will have global consequences, including sea level rise of possibly more than 1 meter in this century (and much more afterward) and by a reduced ability to naturally reflect incoming solar energy—which would lead to further heating by absorption on land and at sea as the ice pack retreats.

Surface Insights of Mesoporous Fragile Organic Materials Under Ultra‐Low‐Voltage Directed by Gemini Column

AbstractMesoporous materials find widespread applications due to their high specific surface area, contributing to enhanced performance. Scanning electron microscopy (SEM) observation of mesoporous materials provides valuable insights into their mesostructures. However, direct observation of the outermost surfaces, which often dictate material properties, remains challenging, especially for highly insulating and fragile compounds. In this study, utilizing SEM observation with ultra‐low‐voltage acceleration directed by Gemini column is proposed to achieve direct surface imaging of mesoporous organic materials with highly insulating and fragile characteristics. By observing mesostructured polymers obtained through a soft‐templating method without washing, stuffed pores are identified allowing the differentiation of micelle templates and polymer walls. Moreover, leveraging SEM measurements, a polymerization mechanism is proposed for dopamine on the polymer micelles adhered to the graphene oxide nanosheets. These findings demonstrate the potential of SEM measurements with ultra‐low accelerating voltage in facilitating surface observations of polymer‐derived nanomaterials characterized by high insulating properties and a fragile framework.

Impact of Assimilating Radar Solid Precipitation Data in the Canadian Precipitation Analysis System

Abstract The Canadian Precipitation Analysis (CaPA) system provides near-real-time precipitation analyses over Canada by combining observations with short-term numerical weather prediction forecasts. CaPA’s snowfall estimates suffer from the lack of accurate solid precipitation measurements to correct the first-guess estimate. Weather radars have the potential to add precipitation measurements to CaPA in all seasons but are not assimilated in winter due to radar snowfall estimate imprecision and lack of precipitation gauges for calibration. The main objective of this study is to assess the impact of assimilating Canadian dual-polarized radar-based snowfall data in CaPA to improve precipitation estimates. Two sets of experiments were conducted to evaluate the impact of including radar snowfall retrievals, one set using the high-resolution CaPA (HRDPA) with the currently operational quality control configuration and another increasing the number of assimilated surface observations by relaxing quality control. Experiments spanned two winter seasons (2021 and 2022) in central Canada, covering part of the entire CaPA domain. The results showed that the assimilation of radar-based snowfall data improved CaPA’s precipitation estimates 81.75% of the time for 0.5-mm precipitation thresholds. An increase in the probability of detection together with a decrease in the false alarm ratio suggested an improvement of the precipitation spatial distribution and estimation accuracy. Additionally, the results showed improvements for both precipitation mass and frequency biases for low precipitation amounts. For larger thresholds, the frequency bias was degraded. The results also indicated that the assimilation of dual-polarization radar data is beneficial for the two CaPA configurations tested in this study.

Site‐Specific Multiple Stressor Assessments Based on High Frequency Surface Observations and an Earth System Model

AbstractGlobal Earth system models are often enlisted to assess the impacts of climate variability and change on marine ecosystems. In this study, we compare high frequency (daily) outputs of potential ecosystem stressors, such as sea surface temperature and surface pH, and associated variables from an Earth system model (GFDL ESM4.1) with high frequency time series from a global network of moorings to directly assess the capacity of the model to resolve local biogeochemical variability on time scales from daily to interannual. Our analysis indicates variability in surface temperature is most consistent between ESM4.1 and observations, with a Pearson correlation coefficient of 0.93 and bias of 0.40°C, followed by variability in surface salinity. Physical variability is reproduced with greater accuracy than biogeochemical variability, and variability on seasonal and longer time scales is more consistent between the model and observations than higher frequency variability. At the same time, the well‐resolved seasonal and longer timescale variability is a reasonably good predictor, in many cases, of the likelihood of extreme events. Despite limited model representation of high frequency variability, model and observation‐based assessments of the fraction of days experiencing surface T‐pH and T‐Ωarag multistressor conditions show reasonable agreement, depending on the stressor combination and threshold definition. We also identify circumstances in which some errors could be reduced by accounting for model biases.

Effect of the Ni plating on Al–Cu dissimilar metal laser welded joint

In this study, the joint strength and interfacial microstructure of Al–Cu laser welded joints are investigated to understand the effect of Ni plating. Cu without plating and Cu plated with 1 μm and 4 μm of Ni were laser welded with Al, respectively, and their differences in joint strength and microstructure were comparatively analyzed. Macrostructure observations showed that the plating had no effect on the change of weld pool shape. Lap shear tests revealed that there was a distinctive improvement in joint strength with the Ni plating. Under a 1.4 kW laser power condition, it was noted that the sample with 4 μm Ni plating showed a 49% increase in load and a 100% increase in elongation compared to the sample without plating. Fracture surface observations revealed that Ni addition has changed the crack propagation path resulting in the increased joint strength. Microstructural analysis showed that the Ni is occupied in intermetallic compounds (IMCs) such as Al3Cu2, AlCu, and Al2Cu3 developed at the interface between Cu and Al2Cu which were known as the primary crack propagation phase in Al–Cu laser welded joint. Additionally, increases in their thickness and changes in their shapes to irregular wavy forms were observed, potentially reducing load concentration and increasing joint surface area, facilitating stable joint formation. Density functional theory calculations showed that the IMCs with Ni undergo contraction in the cell volume suggesting solid solution strengthening of IMCs by Ni addition.

Refined GEDI Level-2A Database Construction: Focused on Gyeonggi Province, Republic of Korea

The Global Ecosystem Dynamics Investigation (GEDI), a full-waveform light detection and ranging system, translated the energy into a continuous waveform and recorded the signals chronologically for enabling geometric analysis of the vertical structure of vegetation. The National Aeronautics and Space Administration has used the land, vegetation, and ice sensor (LVIS) airborne laser altimeter system to measure terrain, tree heights, and vegetation carbon stocks in designated areas. The effectiveness of the collected LVIS data has been proven in mapping forest structures and biomass in tropical and temperate systems. Based on the successful achievements of LVIS, the GEDI aimed to establish a global range of forest data needed to analyze and predict the carbon cycle and climate change. The GEDI was launched aboard the SpaceX-16 in 2018 and successfully attached to the International Space Station (ISS) for a 2-year mission, but now extended until March 2023. Since being mounted on the ISS, GEDI measured over 10 billion cloud-free surface observations within the range of 51.6°N to 51.6°S. In this paper, GEDI mission is introduced, and the process of downloading, refining the GEDI level-2A product focused on Gyeonggi Province is outlined.