Variations In Surface Topography Research Articles

Flood depth mapping in street photos with image processing and deep neural networks

Many parts of the world experience severe episodes of flooding every year. In addition to the high cost of mitigation and damage to property, floods make roads impassable and hamper community evacuation, movement of goods and services, and rescue missions. Knowing the depth of floodwater is critical to the success of response and recovery operations that follow. However, flood mapping especially in urban areas using traditional methods such as remote sensing and digital elevation models (DEMs) yields large errors due to reshaped surface topography and microtopographic variations combined with vegetation bias. This paper presents a deep neural network approach to detect submerged stop signs in photos taken from flooded roads and intersections, coupled with Canny edge detection and probabilistic Hough transform to calculate pole length and estimate floodwater depth. Additionally, a tilt correction technique is implemented to address the problem of sideways tilt in visual analysis of submerged stop signs. An in-house dataset, named BluPix 2020.1 consisting of paired web-mined photos of submerged stop signs across 10 FEMA regions (for U.S. locations) and Canada is used to evaluate the models. Overall, pole length is estimated with an RMSE of 17.43 and 8.61 in. in pre- and post-flood photos, respectively, leading to a mean absolute error of 12.63 in. in floodwater depth estimation. Findings of this research are sought to equip jurisdictions, local governments, and citizens in flood-prone regions with a simple, reliable, and scalable solution that can provide (near-) real time estimation of floodwater depth in their surroundings.

Study the variation of surface topography & corrosion resistance of Cr-GO nanocomposite coatings by addition of GO nanoparticles

The chromium-graphene oxide nanocomposite coating was synthesized successfully by the electroplating method in this investigation. The influence of the addition of GO on surface topography, microhardness and the corrosion behavior of chromium coatings was studied by polarization and electrochemical impedance microscopy methods. The maximum surface microhardness value was measured at a sample with 10 wt% of GO particle equals to 766 HV. The results of surface analysis (Atomic Force Microscopy and microhardness) reveals that the combination of two main factors of GO particle addition and coating thickness has more effect on the surface microhardness than the grain size of topographies. Corrosion results show the addition of the GO particles reduces the corrosion resistance of chromium coating but layer with 5 wt% of GO particles has better corrosion resistance than other composite coatings. Also, results show that corrosion resistance has a meaningful relationship with Sa/Sp ratio.

Multifeature Extraction of Three‐Dimensional Topography of Carbon Steel Specimen during Fatigue Process

In order to investigate the variation of three‐dimensional metal surface topography during fatigue process, a three‐dimensional (3D) topography acquisition platform was built with an in situ tensile tester and a three‐dimensional profilometer. Q235 steel specimens were chosen as research objects, and the three‐dimensional surface topography information at various stages of fatigue damage was obtained. Through the characterization of three‐dimensional roughness, combined with surface height distribution and multifractal analysis, the variations of metal surface topography in the fatigue process were described. Results show that the arithmetic mean deviation of the surface (Sa), the width of the multifractal spectrum (Δα), and the mean value of surface height distribution (μ) and its standard deviation (δ) increase nonlinearly with the increase of fatigue cycles. The rate of fatigue damage is slow in the early stage and high in the middle and late stages. The surface height distribution amplitude (A) decreases with the increase of fatigue cycles, which indicates that the height data concentration decreases, and the metal surface becomes uneven. The Bayesian data fusion method was applied to establish a nonlinear mapping between the topography features and the damage, with the above five characteristic parameters (Sa, Δα, A, μ, and δ) as the data layer. Finally, a surface topography feature fusion method is proposed, and a case study is conducted to verify its applicability. The research results can provide reference for fatigue damage assessment.

Active transfer faulting in the NW Sub-Himalaya (India) observed by space-borne topographic analyses

The results of surface morphology and InSAR analyses carried out along a NNE-SSW oriented (~7 km-long) transfer fault are presented. This structure actively accommodates differential motion across two blocks in the western Sub-Himalayan belt of India. Segmentation is most pronounced in this sector of the accretionary wedge, where minimal climatic variations and a three-fold sub-division (Kangra Renetrant-Nahan Salient-Dehradun Reentrant) are well recognized. Segmentation is here clearly elucidated by variation in surface topography, geologic structure and recorded seismicity over the last few decades. However, the transition from one segment to another is poorly documented and understood. This article primarily documents surface topography and drainage anomalies within the transition zone between the Kangra Reentrant and the Nahan Salient through the study of space imageries spanning nearly six-decades (i.e. early 1960's to present). Geomorphic observations and InSAR analyses demonstrate that the segmentation is largely governed by lateral variation in geological structure, deformation patterns and mechanical stratigraphy and accommodated by transverse movement along the transfer fault. It should be noted that transfer faults commonly represent a privileged pathway for the major drainage and therefore surface manifestations are rarely preserved, e.g. Yamuna Tear, Ganga Tear etc. A rare instance of preserved surface topography associated with the recent activity along the Sabilpur transfer fault at the transition between the Kangra Renetrant and the Nahan Salient is documented here. Our investigations demonstrate that the Sabilpur Active Fault (SAF) accommodates differential tectonic convergence between the two blocks predominantly by left-lateral strike-slip kinematics with a component of uplift related to thrusting at HFT.

Simulation of Topography Effects on Rockfall‐Generated Seismic Signals: Application to Piton de la Fournaise Volcano

AbstractSeismic waves generated by rockfalls contain valuable information on the properties of these events. However, as rockfalls mainly occur in mountainous regions, the generated seismic waves can be affected by strong surface topography variations. We present a methodology for investigating the influence of topography using a Spectral‐Element‐based simulation of 3‐D wave propagation in various geological media. This methodology is applied here to Dolomieu crater on the Piton de la Fournaise volcano, Reunion Island, but it can be used for other sites, taking into account local topography and medium properties. The complexity of wave fields generated by single‐point forces is analyzed for different velocity models and topographies. Ground‐motion amplification is studied relative to flat reference models, showing that Peak Ground Velocity (PGV) and total kinetic energy can be amplified by factors of up to 10 and 20, respectively. Simulations with Dolomieu‐like crater shapes suggest that curvature variations are more influential than depth variations. Topographic effects on seismic signals from rockfalls at Dolomieu crater are revealed by interstation spectral ratios. Results suggest that propagation along the topography rather than source direction dominates the spectral ratios and that resulting radiation patterns can be neglected. The seismic signature of single rockfall impacts is studied. Using Hertz contact theory, impact force and duration are estimated and then used to scale simulations, achieving order‐of‐magnitude agreement with observed signal amplitudes and frequency thresholds. Our study shows that combining Hertz theory with high‐frequency seismic wave simulations on real topography improves the quantitative analysis of rockfall seismic signals.

An improved process for the fabrication and surface treatment of custom-made titanium cranioplasty implants informed by surface analysis.

Cranioplasty implants are routinely fabricated from commercially pure titanium plates by maxillofacial prosthetists. The differing fabrication protocols adopted by prosthetists working at different hospital sites gives rise to considerable variations in surface topography and composition of cranioplasty implants, with residues from the fabrication processes having been found to become incorporated into the surface of the implant. There is a growing recognition among maxillofacial prosthetists of the need to standardise these protocols to ensure quality and consistency of practice within the profession. In an effort to identify and eliminate the source of the inclusions associated with one such fabrication protocol, the present study examined the surfaces of samples subjected to each of the manufacturing steps involved. Surface and elemental analysis techniques identified the main constituent of the surface inclusions to be silicon from the glass beads used to texture the surface of the implant during fabrication. Subsequent analysis of samples prepared according to a revised protocol resulted in a more homogeneous titanium dioxide surface as evidenced by the reduction in area occupied by surface inclusions (from 8.51% ± 2.60% to 0.93% ± 0.62%). These findings may inform the development of improved protocols for the fabrication of titanium cranioplasty plates.

Evaluation of passive microwave melt detection methods on Antarctic Peninsula ice shelves using time series of Sentinel-1 SAR

Passive microwave datasets have been used to quantify the extent and duration of surface melt in Greenland and Antarctica from 1978 on with daily and near-daily intervals. These results have important implications for climate analysis and may help evaluate ice shelf stability. However, the accuracy of passive microwave methods used to detect melt is difficult to quantify, especially on the Antarctic Peninsula. Here four different melt detection methods are employed, including a new formulation of a statistical analysis of brightness temperature time series using a K-means clustering algorithm. Strikingly, two of the most widely used passive microwave melt detection methods are found to vary by 48% mean days of melt per year across six different locations on the Larsen C, Wilkins, and George VI Ice Shelves. In the absence of ground truth observations, time series of Sentinel-1 SAR observations from 2016 on provide a comparison dataset. In topographically flat regions where surface melt is spatially uniform, the passive microwave melt detection method based on a K-means analysis and the cross-polarization gradient ratio method demonstrate the highest agreement and correlation with active radar melt detection methods. One issue which has plagued passive microwave analysis is its coarse spatial resolution. High resolution SAR images are able to demonstrate and quantify the spatial variability of melt within individual passive microwave pixels. Melt is shown to be suitably uniform in space for passive microwave applications at the study sites on Antarctic Peninsula ice shelves, but not so in other regions of the Antarctic Peninsula. Spatial heterogeneity of surface melt on the sub-pixel scale is often related to varying surface topography.

Application of Machine Learning-Based Electrochemical Deposition Models to CMP Modeling

Chemical mechanical polishing/planarization (CMP) is the primary process used for modern integrated circuits (IC) manufacturing. Modeling of the post-CMP surface profile is critical for detecting planarity hotspots prior to manufacturing and avoiding fatal failures of chips. Electrochemical deposition (ECD) is a key process for the void-free filling of interconnection wires and vias in modern chips. Large surface topography variations generated after ECD affect the post-CMP surface profile. In this paper, several machine learning approaches are used to model surface profiles after ECD that are used as input to CMP models. Different combinations of deep neural networks, long-shortterm-memory (LSTM) recurrent networks, convolutional neural networks and XGBoost algorithms are investigated and compared. The model based on the XGBoost library showed superior performance and accuracy

Tribological performance of non-asbestos brake friction material in contact with brake disc of varying topography

PurposeThe purpose of this paper is to evaluate experimentally the influence of different surface roughness of the contacting disc on tribological performance of the non-asbestos brake friction material (BFM).Design/methodology/approachTaguchi method was applied to design an experiment using three different discs of gray cast iron with different surface roughness, which is measured using optical profilometer. These discs were subjected to sliding against pins prepared with the developed non-asbestos BFM, using pin on disc friction and wear monitor.FindingsThe experimental results shows that the disc 2 (Ra = 3.77µm) gives wear of 22.78µm and coefficient of friction of 0.462, which is recommended for extreme brake performance. Analysis of Taguchi design revealed that the disc surface was most significant parameter among the parameters under study.Practical implicationsDuring braking, continuous sliding between the BFM and brake disc or drum not only results into wear of BFM but also changes the surface finish of the brake drum or disc. This leads to variation in surface topography of the drum or disc surface with application of brakes, which further affects the characteristics of the BFM.Originality/valueThe tribological performance of BFM depends upon the topography of the surface on which it was sliding. To get best performance of the non-asbestos friction materials, disc having moderate surface finish is recommended. Scanning electron microscope micrographs had shown the different plateaus formed and energy-dispersive X-ray spectroscopy spectra identified presence of different chemical elements prior to sliding of the pins surface over different discs surface topography.Peer reviewThe peer review history for this article is available at:https://publons.com/publon/10.1108/ILT-04-2020-0120/

On the dynamics of a lubricated roller contact

This study proposes a dynamic model of a lubricated roller contact, focusing on the excitation of surface pit/defect. The fluctuation of contact force caused by periodic surface topography variation is used to determine the dynamic displacements and velocities of contact bodies. These responses, in turn, affect the thickness and flow of lubrication film, impacting contact pressure, and consequently contact force that is required in the dynamic analysis. It is shown, as the pit size grows, the acceleration increment escalates, therefore, can be used as an effective indicator for pitting failure occurrence. Additionally, a comparison of contact pressure between dynamic simulation and its quasi-static counterpart points to the importance of dynamic responses in tribological behavior description.

Evaluating integrated surface/subsurface permafrost thermal hydrology models in ATS (v0.88) against observations from a polygonal tundra site

Abstract. Numerical simulations are essential tools for understanding the complex hydrologic response of Arctic regions to a warming climate. However, strong coupling among thermal and hydrological processes on the surface and in the subsurface and the significant role that subtle variations in surface topography have in regulating flow direction and surface storage lead to significant uncertainties. Careful model evaluation against field observations is thus important to build confidence. We evaluate the integrated surface/subsurface permafrost thermal hydrology models in the Advanced Terrestrial Simulator (ATS) against field observations from polygonal tundra at the Barrow Environmental Observatory. ATS couples a multiphase, 3D representation of subsurface thermal hydrology with representations of overland nonisothermal flows, snow processes, and surface energy balance. We simulated thermal hydrology of a 3D ice-wedge polygon with geometry that is abstracted but broadly consistent with the surface microtopography at our study site. The simulations were forced by meteorological data and observed water table elevations in ice-wedge polygon troughs. With limited calibration of parameters appearing in the soil evaporation model, the 3-year simulations agreed reasonably well with snow depth, summer water table elevations in the polygon center, and high-frequency soil temperature measurements at several depths in the trough, rim, and center of the polygon. Upscaled evaporation is in good agreement with flux tower observations. The simulations were found to be sensitive to parameters in the bare soil evaporation model, snowpack, and the lateral saturated hydraulic conductivity. Timing of fall freeze-up was found to be sensitive to initial snow density, illustrating the importance of including snow aging effects. The study provides new support for an emerging class of integrated surface/subsurface permafrost simulators.

High-resolution lithosphere viscosity structure and the dynamics of the 2008 Wenchuan earthquake area: new constraints from magnetotelluric imaging

SUMMARY Estimation of lithospheric viscosity remains challenging, especially for variations with spatial scales less than 100 km. Some recent studies have developed a method to determine viscosity structure from electrical conductivity models determined from magnetotelluric (MT) data. This method was initially applied to the extensional transition zone from the Great Basin to Colorado Plateau. Here, we use this approach to infer the effective lithospheric viscosity in a convergent setting by using an MT profile that crosses the eastern margin of the Tibetan Plateau. The profile extends from the Songpan-Ganzi block, crosses the 2008 Wenchuan earthquake epicentre region and ends in the Sichuan basin. The preferred viscosity structure is characterized by the middle-lower crustal viscosities in the range 2.42 × 1018 to 2.69 × 1021 Pa s below the Songpan-Ganzi block. In the Longmenshan fault zone and 2008 Wenchuan Ms8.0 earthquake area, the crustal viscosity is higher and in the range 4.32 × 1018 to 5.10 × 1021 Pa s with significant small-scale (<100 km) lateral variations. The MT-derived viscosities are consistent with previous regional-scale estimates but reveal the viscosity structure in more detail. The preferred geodynamic model can explain both the crustal deformation velocity and the small-scale lateral variations of surface topography. It implies that the crustal deformation is driven by mantle flow that results in a weak coupling of the upper and middle-lower crust beneath the eastern Tibetan Plateau. The inferred viscosity structure may help further understand the earthquake mechanisms in the Longmenshan fault zone.

Surface and subsurface modifications of AA7075-T6 induced by dry and cryogenic high speed machining

The high speed machining process is considered as one of the manufacturing technologies more prone to increase the productivity. The increasing interest in this manufacturing process is also due to the good surface quality (e.g. low roughness) as well as the significant alteration of the subsurface (improved hardness and microstructure refinement) of the machined parts. This paper describes the metallurgical phenomena occurring during high speed turning performed under dry and cryogenic conditions on aluminium alloy AA7075 T6 and investigates their effects on the surface integrity. Two cutting parameters, namely cutting speed and feed rate, were varied to induce surface and subsurface changes, such as microstructure and surface topography variation as well as mechanical properties modifications. The surface integrity was analysed through optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), surface roughness and micro-hardness measurements.

Heat transfer and flow performance in additively manufactured cooling channels with varying surface topography

The flexibility in respect of design and manufacturing freedom that additive manufacturing (AM) offer are key driving factors for many industrial scctors. For example, designing and manufacturing u ...

Topography-Driven Shape, Spread, and Retention of Leaf Surface Water Impacts Microbial Dispersion and Activity in the Phyllosphere

To study the impact of lateral variation in surface topography on the microbial colonization of plant leaves, we used a two-step casting process to generate topomimetic “replicasts” in polydimethylsiloxane which faithfully resembled leaf surface topography at submicrometer scale. This process revealed that the shape and size of the phyllotelma—the collective body of standing water on a leaf surface—was a function of wetting method and presence of surface features, in particular leaf veins. The use of dyes and fluorescently labeled bacteria showed that these veins, especially on the abaxial side, contributed to the pooling, retention, and lateral spread of water and microorganisms. Bodies of water along veins acted as conduits that allowed bacterial cells to sense chemicals over distances exceeding their body length by four orders of magnitude. Bacterial survival rates under conditions of low relative humidity were twice as high on leaf replicasts as on flat surfaces, suggesting topography-dependent protection from desiccation. Our findings highlight the need for greater quantitative understanding of the impact of leaf surface topography on phyllotelma connectivity and the outcomes of interactions between microorganisms and with their plant host. Such understanding benefits both theory and practice of phyllosphere microbiology in areas such as foliar disease management and food safety of leafy greens.

Role of roughness levels induced by the laser texturing on the wettability behaviour of ABS

The development of patterned surfaces to induce different wettability behavior on industrial components has recently gained attention due to their potential applications, for example anti-icing, anticondensation and superoleophobicity, among others. However, limited semi empirical studies have been reported on the study of a general predictive formula that considers all possible wetting states of a droplet.This study is focused on validating a theoretical expression as a predictive tool for future wettability modification based solely on the surface topography variation using experimental data. Understanding the effects of surface modifications, produced by direct ultrashort laser texturing on the wettability properties of Acrylonitrile Butadiene Styrene (ABS) is wanted. The present study is a preliminary work that will be as an introduction for future studies regarding the wettability modification of different thermoplastics.

Surface features and flotation behaviors of spodumene as influenced by acid and alkali treatments

Surface dissolution was proved as a fundamental phenomenon in the flotation of spodumene. This study presents an improved understanding of surface dissolution behavior and the corresponding surface states involving consideration of topography, chemical species distribution, as well as oleate adsorption at spodumene surface treated by sodium hydroxide (NaOH) and hydrochloric acid (HCl). Micro-flotation results showed that spodumene flotation was activated with NaOH treatment but was depressed with HCl treatment when sodium oleate was used as a collector. AFM imaging revealed variations in surface topography, indicative of different dissolution behaviors. Water rinsing treatment increased flotation response of NaOH-treated spodumene but had no effect in the case of HCl treatment. Colloidal substances precipitated at surface conditioned in NaOH solution as evidenced from in-situ AFM, and appeared to be unfavorable for oleate adsorption. Chemical states of elements at surface were influenced by treatments, and larger relative contents of Al and unsaturated Al at surface with NaOH treatment were revealed by XPS as compared with that treated by HCl. Density functional theory calculations indicated that unsaturated Al was favorable for oleate adsorption. It seems the relative content of unsaturated Al at surface influenced by acid and alkali treatments dominates the extent of oleate adsorption.

Assessing the effects of sea-state related errors on the precision of high-rate Jason-3 altimeter sea level data

Abstract The investigation of ocean surface topography variation by low-resolution mode (LRM) altimeters at length scales shorter than 100 km is limited by cm-scale measurement noise. Spectral analysis of along-track altimeter data has been used to highlight the issue and to illustrate that one significant noise source stems from correlation between significant wave height (SWH) and range errors that is inherent to any waveform retracking algorithm. This paper focuses on improved characterization and reduction of these high-rate correlated errors that arise from this altimeter measurement process. Specifically, it addresses the effects of sea-state related errors in high rate (20-Hz) Jason-3 satellite sea level data that may possibly impact both short-scale and longer-scale data via interplay with the sea state bias (SSB) correction. Among the suite of standard corrections used to extract sea surface height (SSH) from the raw altimeter range, the empirical SSB term is designed to remove correlation between range and SWH measurements, but not explicitly short-scale error between the two. In this paper, we report that the efficacy of the SSB correction varies with wavelength and it does not remove all correlated signal at high wavenumbers. Following several recent studies, an independent high-frequency adjustment (HFA) is developed to remove these residual correlated errors. Both SSB and HFA are applied on SSH estimations at the 20-Hz rate, improving both 20-Hz and 1-Hz data. Jason-3 data are used as a test bed. Both corrections and net results are specific to MLE4 Jason-3 waveform retracking. Because the reported updated SSB models provide nearly unbiased continuity from Jason-1 to Jason-3 SSB time-series and the MLE4 retracking algorithm is the standard for these missions, the Jason-3 HFA solution can be applied to earlier Jason data with implications for improving the combined 16-year Jason record. By design, the HFA does not impact wavelengths greater than 200 km which is the acting domain of the SSB correction. Applying both the SSB and HFA corrections leads to a global SSH variance reduction nearing 35% in average. The SSH denoising approach through the computation of an additional HFA term is applicable for any LRM ocean altimeter.

Underwater Superoleophobic Crucian Fish Scale: Influence of Ontogeny on Surface Morphologies and Wettability

Recent development concerning underwater superoleophobic surface has been motivated by fish scales, which are rendered capable of preventing their surfaces from contamination in oil-polluted water. In this paper, for the first time, the variations in surface topography and chemical composition of crucian fish scales at different growth stages have been investigated. The water and oil contact angles, surface morphology and chemical composition of the fish scales were measured by means of contact angle measurements, scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. It is found that surface morphology and chemical composition both have influences on surface wettability of fish scales; fish scale at infant period seems to possess better hydrophilicity than that of fish scales at mature and senescent period. What is more, it is believed that the wettability heavily depends on the surface structures during their growth procedure, which enlightens us to design and fabricate biomimetic multifunctional underwater superoleophobic surfaces inspired by nature.

Influence of the electrical parameters of the anodizing PEO process on wear and corrosion resistance of niobium

In this work, anodic coatings were obtained on niobium by plasma electrolytic oxidation (PEO). Surface topography variation depending on the electrical perturbation mode of the PEO process was evidenced. Coatings obtained at galvanostatic mode exhibited the formation of circular pores with no variation in morphology distribution with current density. Meanwhile, the coatings obtained under a galvanostatic - potentiostatic condition exhibited different topographies according to the potential applied and better corrosion and wear resistance. Most of the coatings showed breakdown potential and formation of sparks at approx. 260 V. However, coating obtained at 300 V exhibited the formation of a compact structure with good tribological performance (30 times better than that of the substrate (Wear rate 0.9 × 10−9 kg/N.m) and high corrosion resistance due to low porosity (Rp = 10.52 Mohm cm2).