Rough Topography Research Articles

Estimation of the friction coefficient by identifying the evolution of rough surface topography

The complexity and randomness of surface roughness make the origin of friction always puzzling. Is there a potential correlation mechanism between the evolution of friction force and surface topography, and is it possible to estimate the friction coefficient from the topography evolution? Here, we explore the evolution of surface topography in metallic materials during friction by defining the characteristic orientation of the surface and analyzing its changes over time, which closely mirrors the behavior of friction forces. Then, we propose a simple relationship that relates the characteristic orientation and friction force via the friction coefficient. Therefore, the friction coefficient can be evaluated based on topography evolution without relying on any theoretical modeling assumptions. These results reveal the mechanism between complex surface topography and friction force through a simple formula and provide a method to estimate the friction coefficient. This method has promising applications when the friction coefficient is difficult to measure, such as in large-scale landslides and geologic faults.

Molecular dynamics investigation of nano-polishing on silicon carbide substrate with rough topography using a rotating diamond abrasive

To achieve low-damage polishing on silicon carbide substrates utilizing a rotating diamond abrasive, the molecular dynamics model for nano-polishing is established. The nano-polishing simulation of silicon carbide substrates with both smooth and rough topographies is conducted using the diamond abrasive at two different velocity ratios. The constructed MD models are compared with existing models to assess the influence of abrasive rotation and substrate topography. The results provide valuable insights into the nano-polishing. Firstly, improving substrate smoothness and increasing abrasive rotation can effectively reduce von Mises stress, force, temperature, and amorphous layer thickness. Secondly, the atomic motion within silicon carbide substrates is affected by abrasive rotation and substrate topography, thus altering the removal mechanism. Finally, the differences in friction coefficient between the constructed MD models and existing models arise from atomic adhesion and plie-up phenomena.

A New Numerical Simulation Method for 3D Rough Surface Topography of Shot Peening Parts with Specified 3D Roughness Spatial Parameters

A New Numerical Simulation Method for 3D Rough Surface Topography of Shot Peening Parts with Specified 3D Roughness Spatial Parameters

The Rapid Response of Southern Ocean Biological Productivity to Changes in Background Small Scale Turbulence

AbstractBackground subsurface vertical mixing rates in the Southern Ocean (SO) are known to vary by an order of magnitude temporally and spatially, due to variability in their generating mechanisms, which include winds and shear instabilities at the surface, and the interaction of tides and lee waves with rough bottom topography. There is great uncertainty in the parameterization of this mixing in coarse resolution Earth System Models (ESM), and in the impact that this has on SO biological productivity on sub decadal timescales. Using a data assimilating biogeochemical ocean model we show that SO phytoplankton productivity is highly sensitive to differences in background diapycnal mixing over short timescales. Changes in the background vertical mixing rates alter key biogeochemical and physical conditions. The greatest changes to the distribution of physical and biogeochemical tracers occur in regions with very strong tracer vertical gradients. A combination of reduced nutrient limitation and reduced light limitation causes a strong increase in SO phytoplankton productivity with higher background mixing. This leads to increased summer carbon export but reduced wintertime export over the mixed layer depth, which could alter the strength of the SO biological carbon pump and atmospheric concentrations on centennial to millennial timescales. This study demonstrates the importance of accurately representing diapycnal mixing in ESM to predict SO biogeochemical dynamics and their broader climatic implications.

Multiple states of two-dimensional turbulence above topography

The recent work of Siegelman & Young (Proc. Natl Acad. Sci. USA, vol. 120, issue 44, 2023, e2308018120) revealed two extreme states reached by the evolution of unforced and weakly damped two-dimensional turbulence above random rough topography, separated by a critical kinetic energy $E_\#$ . The low- and high-energy solutions correspond to topographically locked and roaming vortices, surrounded by non-uniform and homogeneous background potential vorticity (PV), respectively. However, we found that these phenomena are restricted to the particular intermediate length scale where the energy was initially injected into the system. Through simulations initialized by injecting the energy at larger and smaller length scales, we found that the long-term state of topographic turbulence is also dependent on the initial length scale and thus the initial enstrophy. If the initial length scale is comparable to the domain size, the long-term flow field resembles the minimum-enstrophy state proposed by Bretherton & Haidvogel (J. Fluid Mech., vol. 78, issue 1, 1976, pp. 129–154), with very few topographically locked vortices; the long-term enstrophy is quite close to the minimum value, especially when the energy is no larger than $E_\#$ . As the initial length scale becomes smaller, more vortices nucleate and become more mobile; the long-term enstrophy increasingly deviates from the minimum value. Simultaneously, the background PV tends to homogenization, even if the energy is below $E_\#$ . These results complement the phenomenology of topographic turbulence documented by Siegelman & Young, by showing that the minimum-enstrophy and background PV homogenization states can be adequately approached by large- and small-scale initial fields, respectively, with relatively arbitrary energy.

Enhanced generation of internal tides under global warming

A primary driver of deep-ocean mixing is breaking of internal tides generated via interactions of barotropic tides with topography. It is important to understand how the energy conversion from barotropic to internal tides responds to global warming. Here we address this question by applying a linear model of internal tide generation to coupled global climate model simulations under a high carbon emission scenario. The energy conversion to high-mode internal tides is projected to rise by about 8% by the end of the 21st century, whereas the energy conversion to low-mode internal tides remains nearly unchanged. The intensified near-bottom stratification under global warming increases energy conversion into both low and high-mode internal tides. In contrast, the intensified depth-averaged stratification reduces the modal horizontal wavenumber of internal tides, leading to increased (decreased) energy conversion into high (low)- mode internal tides. Our findings imply stronger mixing over rough topography under global warming, which should be properly parameterized in climate models for more accurate projections of future climate changes.

A decision-making framework to maximise the evolutionary potential of populations - Genetic and genomic insights from the common midwife toad (Alytes obstetricans) at its range limits

Anthropogenic habitat modification and climate change are fundamental drivers of biodiversity declines, reducing the evolutionary potential of species, particularly at their distributional limits. Supportive breeding or reintroductions of individuals are often made to replenish declining populations, sometimes informed by genetic analysis. However, most approaches utilised (i.e. single locus markers) do not have the resolution to account for local adaptation to environmental conditions, a crucial aspect to consider when selecting donor and recipient populations. Here, we incorporate genetic (microsatellite) and genome-wide SNP (ddRAD-seq) markers, accounting for both neutral and putative adaptive genetic diversity, to inform the conservation management of the threatened common midwife toad, Alytes obstetricans at the northern and eastern edges of its range in Europe. We find geographically structured populations (n = 4), weak genetic differentiation and fairly consistent levels of genetic diversity across localities (observed heterozygosity and allelic richness). Categorising individuals based on putatively adaptive regions of the genome showed that the majority of localities are not strongly locally adapted. However, several localities present high numbers of private alleles in tandem with local adaptation to warmer conditions and rough topography. Combining genetic diversity and local adaptations with estimates of migration rates, we develop a decision-making framework for selecting donor and recipient populations which maximises the geographic dispersal of neutral and putatively adaptive genetic diversity. Our framework is generally applicable to any species, but especially to amphibians, so armed with this information, conservationists may avoid the reintroduction of unsuitable/maladapted individuals to new sites and increase the evolutionary potential of populations within species.

A LDH-Derived Metal Sulfide Nanosheet-Functionalized Bioactive Glass Scaffold for Vascularized Osteogenesis and Periprosthetic Infection Prevention/Treatment.

Periprosthetic infection and prosthetic loosing stand out as prevalent yet formidable complications following orthopedic implant surgeries. Synchronously addressing the two complications is long-time challenging. Herein, a bioactive glass scaffold (BGS) functionalized with MgCuFe-layered double hydroxide (LDH)-derived sulfide nanosheets (BGS/MCFS) is developed for vascularized osteogenesis and periprosthetic infection prevention/treatment. Apart from the antibacterial cations inhibiting bacterial energy and material metabolism, the exceptional near-infrared-II (NIR-II) photothermal performance empowers BGS/MCFS to eliminate periprosthetic infections, outperforming previously reported functionalized BGS. The rough surface topography and the presence of multi-bioactive metal ions bestow BGS/MCFS with exceptional osteogenic and angiogenic properties, with 8.5-fold and 2.3-fold enhancement in bone mass and neovascularization compared with BGS. Transcriptome sequencing highlights the involvement of the TGF-β signaling pathway in these processes, while single-cell sequencing reveals a significant increase in osteoblasts and endothelial cells around BGS/MCFS compared to BGS.

A new numerical simulation method of 3D rough surface topography with coupling 3D roughness parameters Sdr, Sdq, Spd, Spc, and characteristic functions

The existing surface topography modeling methods based on random process theory make it difficult to realize the coupling of three-dimensional roughness parameters Sdr, Sdq, Spd, and Spc in ISO25178, which are related to the friction and lubrication performance of parts. The paper proposes constraints set for the structure of spatial features in height matrix discrete points during the random switching process, and the accurate coupling of parameters Sdr, Sdq, Spd, and Spc with characteristic functions is achieved by the improved random switching system. The new method is applied to simulate four kinds of finishing surface topography numerically, and the results show that the relative errors of these four parameters are effectively reduced from 5–110 % to 1 %.

Synthesis of Activated Charcoal from Coconut Shell for the Removal of Crude Oil Spill

Crude oil spills have devastating effects on the environment, particularly aquatic ecosystems. The purpose of the present research is to determine whether dry coconut shells can be used as raw materials to make activated charcoal (AC) via pyrolysis and whether they can be utilized as natural sorbents to clean up crude oil spills. The UV-Vis spectrum of the synthesized CSAC shows distinct peaks at 230 and 260 nm, whereas the activated charcoal exhibits peaks at 231 and 261 nm. The FTIR spectra of the synthesized CSAC reveal a medium broad absorption peak at 3307.2 cm⁻¹, while the raw coconut shell's FTIR spectra show a medium sharp peak at 2945.3 cm⁻¹. The SEM images highlight the unique structural properties of CSAC, showcasing high porosity, varied pore sizes, rough surface topography, and the presence of micropores and mesopores. The chemical activation significantly increased the hydrophobicity of the adsorbent, creating CSAC with a much better adsorption capacity for crude oil removal, having a maximum adsorption capacity of 4840.0 mg/g and the highest percentage of crude oil removal at 99.9985%, as proven by batch experiments for different adsorbent dosages. The batch experimental results indicated that the percentage of crude oil removal increased with an increase in adsorbent dosage and contact time. Based on the correlation coefficients (R²) values (close to unity), it was generally observed that the plots match the Freundlich isotherm better than the Langmuir isotherm model. These findings have made the synthetic CSAC an attractive, useful, and environmentally friendly adsorbent.

Functional ultrasound neuroimaging reveals mesoscopic organization of saccades in the lateral intraparietal area of posterior parietal cortex.

The lateral intraparietal cortex (LIP) located within the posterior parietal cortex (PPC) is an important area for the transformation of spatial information into accurate saccadic eye movements. Despite extensive research, we do not fully understand the functional anatomy of intended movement directions within LIP. This is in part due to technical challenges. Electrophysiology recordings can only record from small regions of the PPC, while fMRI and other whole-brain techniques lack sufficient spatiotemporal resolution. Here, we use functional ultrasound imaging (fUSI), an emerging technique with high sensitivity, large spatial coverage, and good spatial resolution, to determine how movement direction is encoded across PPC. We used fUSI to record local changes in cerebral blood volume in PPC as two monkeys performed memory-guided saccades to targets throughout their visual field. We then analyzed the distribution of preferred directional response fields within each coronal plane of PPC. Many subregions within LIP demonstrated strong directional tuning that was consistent across several months to years. These mesoscopic maps revealed a highly heterogenous organization within LIP with many small patches of neighboring cortex encoding different directions. LIP had a rough topography where anterior LIP represented more contralateral upward movements and posterior LIP represented more contralateral downward movements. These results address two fundamental gaps in our understanding of LIP's functional organization: the neighborhood organization of patches and the broader organization across LIP. These findings were achieved by tracking the same LIP populations across many months to years and developing mesoscopic maps of direction specificity previously unattainable with fMRI or electrophysiology methods.

Spatial and Temporal Variability of Turbulent Mixing in the Deep Northwestern Pacific

AbstractSmall‐scale turbulent mixing supplies potential energy for the upwelling of deep waters in the abyssal ocean, a key component of the global overturning circulation. This process is particularly significant in critical regions such as the Northwestern Pacific where the upwelling structure of deep waters remains poorly understood due to limited knowledge of deep ocean mixing. Here, we investigate the full‐depth spatiotemporal variability of turbulent mixing in the deep Northwestern Pacific based on hydrographic data collected over repeated surveys. Nineteen‐year‐average diapycnal diffusivity of 1.42 × 10−4 m2 s−1 is reveled in the deep Philippine Sea, indicating significantly stronger mixing compared to the stratified ocean interior. Spatially, turbulent mixing strengthens toward the bottom and intensifies westward from the open Pacific to the Philippine Sea due to rough topography. At certain mixing hotspots, enhanced mixing can penetrate up to 2,500 m above the bottom, suggesting a substantial potential for upwelling. Below 2,000 m, turbulent mixing exhibits pronounced seasonal variation that deep mixing is more intense in summer (winter) than in winter (summer) in the West Caroline Basin (the Parece Vela Basin). This spatially varying seasonality may be attributed to the inhomogeneous internal tidal energy dissipation in the Northwestern Pacific. Our study will serve to clarify the modulation of turbulent mixing to deep‐water mass transformation and circulation in the Northwestern Pacific.

Geospatial based soil loss rate and land degradation assessment in Debre Berhan Regio-Politan city, Upper Blue Nile Basin, Central Ethiopia

In Ethiopia’s central highlands, soil erosion and degradation are the most challenging and persistent issues, owing to their rough topography and human activities. Planning land use and managing natural resources, as well as agricultural output, depend on the evaluation of land degradation (LD). Thus, this study was carried out with the objective to quantify and evaluate soil loss rates, sediment yield (SY), and identify degradation hotspot areas in the Debre Berhan Regio-Politan City, Central Highlands of Ethiopia. The city has an area of 127191.7 ha. The Revised Universal Soil Loss Equation (RUSLE) model was applied to generate soil erosion severity map. An empirical equation based on topography was utilized to calculate sediment yield, in addition to the Analytical Hierarchy Process (AHP) method for evaluating land LD. The results showed that the city’s average annual estimated soil loss was 38.5 t ha−1 yr−1. Serious risks of soil loss are especially present in large portions of the city’s hilly eastern, northwest, and north peripheral areas. The city’s yearly average SY varies from 0–32 t ha−1 yr−1, with plain areas generally contributing 0 tons, while the hilly/barren areas contributing 32 tons. The LD severity class indicated that about 15197.65 ha (11.91%), 38018.49 ha (29.85%), 40287.86 ha (31.67%), 19869.97 ha (15.61%), and 13817.73 ha (10.96%) portion is categorized as very low, low, moderate, high, and very high, respectively. To prevent soil loss and LD and increase agricultural productivity, it is crucial to implement nature-based climate-smart agricultural practices and provide capacity-building training in line with the SDGs, Africa Agenda 2063, and national strategies and policies of the country.

Identifying imaging challenges for 1D and 3D geometric complexity (LG space)

In some situations, it is difficult to image seismic data even when factors such as illumination, anisotropy, and attenuation are resolvable. An often-overlooked but dominant factor affecting imaging is the geometric complexity of subsurface reflectors. In some of these settings, we propose that geometric complexity plays a dominant role in the quality of seismic imaging. This has been documented in subsalt regions with poor image quality where 3D vertical seismic profiles (VSPs) are available. VSPs often demonstrate that there is good illumination below salt, but the complexity of the observed downgoing wave and diffractions cannot be simulated with smooth earth models. We use synthetic examples with high geometric complexity and no other complications to analyze the imaging process: a 2D sediment-salt model with rough salt-top topography, and a 1D model with complex reflectivity. In these models, it is difficult to estimate velocity, and it is challenging to image the data. These synthetic examples are useful to understand the limitations of imaging with smooth models, to create guidelines to identify geometric complexity in field data, and to develop possible mitigations to improve imaging. Further real data examples will be needed to test geometric complexity.

Drivers of Land Abandonment in Neelakantha Municipality: Perceptions of Farmers

This study analysed the role of factors for land abandonment in Neelakantha municipality, Dhading. For this purpose, survey and causal-comparative research design are used. Similarly, Reliability and normality of the collected data was ensured by using cronbach alpha and Shapiro-Wilk test respectively. Then after, inferential statistical tools i.e. Pearson correlation and multiple regression analysis have been used to derive the result of the study. This study found that there is a significant impact of high cost of agro product, out migration, rough topography, lack of government protection from international competition, and destruction of food crops by wild animals on land abandonment. However, the impact of irrigation facility and market access on land abandonment was not statistically significant. The findings of the study suggest that the factors that contribute to land abandonment are complex and interrelated. However, the study provides some evidence that the factors that were found to be statistically significant can play a role in land abandonment.

Conformal polishing of a glass microlens array through oxyhydrogen flame-induced viscoelasticity flow at nano/microscale

Glass microlens arrays with small unit sizes and high integration capacities are widely utilized in various optical systems, but the femtosecond laser milling produces microscale residual steps and nanoscale rough topography on microlens surface. Accordingly, an oxyhydrogen flame polishing is proposed after femtosecond laser milling, aiming to efficiently fabricate the ultrasmooth surface without damaging shape accuracy by triggering a viscoelasticity flow at nano/microscale. Through simultaneous modelling of the polishing process, a large thermal power results in a high viscoelasticity flow velocity for nanoscale topography smoothing, followed by microscale step melting. Then, a single-point polishing experiment is conducted to determine the critical transition temperatures for nanoscale smoothing and microscale melting. It is further experimentally applied to achieve an ultrasmooth surface of cylindrical microlens array with its roughness less than 0.2 nm and no hydroxyl introduction. This process also effectively repairs subsurface damage and reduces the form error to ±0.5 μm, improving the surface quality and shape accuracy. Similar results are also observed for the polishing of spherical microlenses. In conclusion, the method of combining femtosecond laser milling and oxyhydrogen flame polishing holds promise for high-efficiency and high-quality fabrication of glass components with micro features.

Involvement of the claustrum in the cortico-basal ganglia circuitry: connectional study in the non-human primate

The claustrum is an ancient telencephalic subcortical structure displaying extensive, reciprocal connections with much of the cortex and receiving projections from thalamus, amygdala, and hippocampus. This structure has a general role in modulating cortical excitability and is considered to be engaged in different cognitive and motor functions, such as sensory integration and perceptual binding, salience-guided attention, top-down executive functions, as well as in the control of brain states, such as sleep and its interhemispheric integration. The present study is the first to describe in detail a projection from the claustrum to the striatum in the macaque brain. Based on tracer injections in different striatal regions and in different cortical areas, we observed a rough topography of the claustral connectivity, thanks to which a claustral zone projects to both a specific striatal territory and to cortical areas involved in a network projecting to the same striatal territory. The present data add new elements of complexity of the basal ganglia information processing mode in motor and non-motor functions and provide evidence for an influence of the claustrum on both cortical functional domains and cortico-basal ganglia circuits.

Development and use of a novel diver-operated ski for surveying nearshore rocky reef habitats.

The use of camera and video technologies for conducting underwater surveys has rapidly expanded over the past several decades. However, the utility of these systems can be significantly hampered by numerous logistical factors, including limited underwater visibility, rough bottom topography, and ease of use for the operator. Video studies can be difficult to compare when methods and terminologies differ. Here, we describe the development of a cost-effective diver-propelled underwater ski-based video system for rapidly acquiring videos in challenging shallow high-energy rocky benthic habitats for quantifying fish, macroalgae, and invertebrates in a coastal temperate system. The ski held the camera at a (relatively) fixed distance from the seafloor, we used parallel lasers to quantify our observations, and we used the standardized language and definitions in the Coastal and Marine Ecological Classification Standard (CMECS) to acquire consistent quantitative data to serve as an ecological baseline, also including archived images. Our results indicate that the ski proved to be an effective tool for capturing insightful data that would otherwise be very difficult and time consuming to collect. Our baseline and repeatable methods can be used by other investigators at this or other locations for monitoring, re-evaluation, or comparisons to other sites.

Vulnerability Assessment of Fallen Trees Along Arterial Road of Bukit Soeharto Grand Forest Park Using Google Street View

The incidence of fallen trees along the roadside was widespread across various locations in Indonesia, particularly in areas where trees naturally thrive. Therefore, this research aimed to explore Google Street View (GSV) to obtain information regarding the potential of fallen trees. A novel approach was proposed using panoramic photos available in GSV data from May 2021 and then subjected to testing along Balikpapan–Samarinda Arterial Road, covering a distance of 33 kilometers (Km), which traversed Bukit Soeharto Grand Forest Park (BSGFP). Leaning trees, trees with imbalanced canopy proportion, dying trees, and trees in rough topography became the criteria specified from GSV photos to determine potentially fallen trees. The results showed that 224 trees along Arterial Road met those criteria, translating to approximately 6.79 trees per kilometer of Arterial Road. The analysis revealed that an imbalance canopy proportion was the primary cause of fallen trees, supported by investigations and comparisons with the corresponding GSV photos before the collapse. The Arterial Road Balikpapan-Samarinda poses moderate fallen tree vulnerability, scoring between 25% and 50%.

Tidal Calibration of the Gladwin Tensor Strain Monitor (GTSM) Array in Taiwan

AbstractTo ensure the accuracy and reliability of crustal strain measures, sensors require a thorough calibration. In Taiwan, the complicated dynamics of surface and subsurface hydrological processes under semi-tropical climate conditions conjugated with the rough surface topography could have impacted strainmeter deployment, pushing the installation conditions astray from the optimal ones. Here, we analyze the complex response of 11 Gladwin Strain Monitor (GTSM) strainmeter type deployed in north and central Taiwan and we propose a novel calibration methodology which relies on waveform modeling of Earth and ocean tidal strain-related deformations. The approach is completely data-driven, starting from a simple calibration framework and progressively adding complexity in the model depending on the quality of the data. However, we show that a simple quasi-isotropic model (three calibration factors) is generally suitable to resolve the orientation and calibration of 8 instruments out of 11. We also highlight the difficulty of clearly defining the behavior of instruments that are highly affected by hydrological forcing.