Variations In Surface Topography Research Articles

Evaluating the impact of ultraviolet C exposure conditions on coliphage MS2 inactivation on surfaces.

The COVID-19 pandemic has raised interest in using devices that generate ultraviolet C (UVC) radiation as an alternative approach for reducing or eliminating microorganisms on surfaces. Studies investigating the efficacy of UVC radiation against pathogens use a wide range of laboratory methods and experimental conditions that can make cross-comparison of results and extrapolation of findings to real-world settings difficult. Here, we use three different UVC-generating sources - a broad-spectrum pulsed xenon light, a continuous light-emitting diode (LED), and a low-pressure mercury vapour lamp - to evaluate the impact of different experimental conditions on UVC efficacy against the coliphage MS2 on surfaces. We find that a nonlinear dose-response relationship exists for all three light sources, meaning that linear extrapolation of doses resulting in a 1-log10 (90%) reduction does not accurately predict the dose required for higher (e.g. 3-log10 or 99.9%) log10 reductions. In addition, our results show that the inoculum characteristics and underlying substrate play an important role in determining UVC efficacy. Variations in microscopic surface topography may shield MS2 from UVC radiation to different degrees, which impacts UVC device efficacy. These findings are important to consider in comparing results from different UVC studies and in estimating device performance in field conditions.

3D Printing and Rapid Replication of Advanced Numerically Generated Rough Surface Topographies in Numerous Polymers

An approach to rapidly produce high‐quality polymer surface topographies from numerically generated surfaces is presented. The approach uses an advanced surface generation tool to flexibly design surfaces with user‐defined topography characteristics over a large range of surface roughness. Roughness instances with root mean square roughness 25, 50, and 100 μm are studied. 3D printing is used to create a master surface and polymer casting and injection molding are employed to enable rapid replication in various polymers. The cross‐correlation ratio (CCR) and a mean difference approach were used to assess replication quality. Injection molding provides high throughput with high replication quality up to CCR ≈ 0.74. While casting in low‐viscosity polymer resins enables slightly improved high‐quality replication (CCR up to ≈0.82) with reduced throughput. Key results include the ability of the 3D‐printed surfaces to replicate tailored variations in surface topography (e.g., amplitude and frequency) and the importance of low viscosity resins in maximizing replication quality in polymer casting. Several interfacial and surface phenomena (both mechanical and biological) are sensitive to surface roughness. The main application lies in providing a valuable tool for research looking at topography influencing phenomena ranging from friction and lubrication to aerodynamic drag, algae growth, and cell growth.

Direct visualization of colloid transport over natural heterogeneous and artificial smooth rock surfaces

Colloid transport in fractured rock formations is an important process impacting the fate of pollutants in the subsurface. Despite intensive and outstanding research on their transport phenomena, the impact of small-scale surface heterogeneity on colloid behavior at the fracture scale remains difficult to assess. In particular, there is relatively little direct experimental evidence on the impact of natural fracture surface heterogeneity on colloid transport. To investigate this, we developed an experimental setup allowing the direct visualization of fluorescent colloid transport in a flow cell containing a natural chalk rock sample while simultaneously monitoring effluent colloid concentrations. We used samples containing both a natural fracture surface and an artificially made smooth surface from the same chalk core. We characterized the roughness and chemical composition of both surface types and numerically calculated each surface's velocity field. From the experiments, we obtained direct images of colloid transport over the surfaces, from which we calculated their dispersion coefficients and quantified the residual deposition of colloids on the rock surface. We also measured the colloid breakthrough curves by collecting eluent samples from the flow cell outlet. The natural fracture surface exhibited larger physical and chemical heterogeneity than the smooth, artificially generated surface. The aperture variability across the natural surface led to preferential flow and colloid transport which was qualitatively apparent in the fluorescent images. The colloid transport patterns matched the calculated velocity fields well, directly linking the surface topography and aperture variation to colloid transport. Compared to the artificially made surface, the natural surface also showed higher dispersion coefficients, which corresponded to the colloids' earlier breakthrough from the flow cell. While we found differences between the elemental composition of the natural and artificially smooth surfaces, we could not observe their impact on the colloids' surface attachment and retention. The main novelty in this work is the coupling of direct colloid transport imaging, breakthrough curve measurements, and colloid surface deposition analyses, in a flow cell containing a natural carbonate rock sample. Our experimental setup can be used to further investigate the link between surface heterogeneity, both chemical and physical, and colloid transport and deposition in natural rock fractures.

Synthesis and characterization of sputter-deposited Ni-rich Ni3Al hard coatings

Ni3Al and Nickel (Ni) rich Ni3Al thin films were deposited on Si (100) substrate by magnetron sputtering and co-sputtering process respectively. Variations in elemental composition, microstructure, surface topography, and mechanical properties were investigated as a function of Ni enrichment via EDS, SEM, AFM, and nanoindentation respectively. Results revealed that the hardness and young’s modulus decrease with increase in Ni content in the film. A maximum hardness of 12.75 GPa was achieved with the elemental composition of Al (20.8 at%) and Ni (79.2 at%). The increase in surface roughness as a result of Ni enrichment led to the increase in hydrophobic properties up to the elemental composition of Al (14.9 at%) and Ni (85.1 at%) beyond which it declined. This study shows that the surface roughness, microstructure, and elemental composition influence the mechanical and hydrophobic properties of the Nickel rich Ni3Al coatings.

Co-localizing Kelvin Probe Force Microscopy with Other Microscopies and Spectroscopies: Selected Applications in Corrosion Characterization of Alloys.

Kelvin probe force microscopy (KPFM), sometimes referred to as surface potential microscopy, is the nanoscale version of the venerable scanning Kelvin probe, both of which measure the Volta potential difference (VPD) between an oscillating probe tip and a sample surface by applying a nulling voltage equal in magnitude but opposite in sign to the tip-sample potential difference. By scanning a conductive KPFM probe over a sample surface, nanoscale variations in surface topography and potential can be mapped, identifying likely anodic and cathodic regions, as well as quantifying the inherent material driving force for galvanic corrosion. Subsequent co-localization of KPFM Volta potential maps with advanced scanning electron microscopy (SEM) techniques, including back scattered electron (BSE) images, energy dispersive spectroscopy (EDS) elemental composition maps, and electron backscattered diffraction (EBSD) inverse pole figures can provide further insight into structure-property-performance relationships. Here, the results of several studies co-localizing KPFM with SEM on a wide variety of alloys of technological interest are presented, demonstrating the utility of combining these techniques at the nanoscale to elucidate corrosion initiation and propagation. Important points to consider and potential pitfalls to avoid in such investigations are also highlighted: in particular, probe calibration and the potential confounding effects on the measured VPDs of the testing environment and sample surface, including ambient humidity (i.e., adsorbed water), surface reactions/oxidation, and polishing debris or other contaminants. Additionally, an example is provided of co-localizing a third technique, scanning confocal Raman microscopy, to demonstrate the general applicability and utility of the co-localization method to provide further structural insight beyond that afforded by electron microscopy-based techniques.

Study on surface properties and fatigue performance of aluminum alloy plate with prestressed ultrasonic peening

Prestressed ultrasonic peening (UP) is beneficial to enlarge bending deformation and improve surface properties of the plate compared to free UP process. The effects of processing parameters on variation of surface topography, surface roughness and hardness, residual stress distribution are analyzed. Then the microstructure and fatigue life with prestressed UP is studied. The results show that smaller surface roughness, larger surface hardness, larger and deeper compressive residual stress are generated in prestressed UP compared to free UP. Small prebending curvature radius and offset distance both contribute to enhancement of surface properties. Large firing pin velocity is beneficial for large surface hardness as well as larger and deeper compressive residual stress; nevertheless, it will increase the surface roughness. The UP process mainly improves the high cycle fatigue life of the material, while there is no difference of the low cycle fatigue life between the peened and un-peened samples. The high cycle fatigue life significantly increases at small stress after peening process and it can be further enhanced after prestressed UP. Deformation band with peened indentations are generated on the surface. With the experiments of distributions for hardness, yield stress and residual stress, the strengthening mechanism in peening process is discussed.

A high precision finite-element forward solver for surface nuclear magnetic resonance incorporating conductivity changes and surface-topography variations

Surface nuclear magnetic resonance (SNMR) is a geophysical method that can be used directly for detecting groundwater resources, and it has attracted the attention of many scholars. In this paper, we propose a new effective algorithm for numerical modeling of 3D SNMR data for arbitrary topography in a conductive medium. We adopt a total-field algorithm for solving the quasi-static variant of Maxwell’s equation and handle a complex-shaped loop source by discretizing the transmitter into electric dipoles, which can be further easily discretized into electric dipoles along the three directions of the Cartesian coordinate system. To solve the 3D SNMR forward-modeling problem quickly and accurately, a new element-integration system based on a new symmetric orthogonal rule is used for calculating the sensitivity (i.e., kernel) functions of all elements. The new rule is based on a special arrangement involving a cubic close-packed lattice structure and is characterized by fast convergence, positive weight, and symmetry. We apply the developed numerical algorithm to SNMR tomography of several typical hydrogeological models. The synthetic results show that higher precision can be achieved with few grids and nodes without increasing the computation time by using the new integration algorithm. In addition, we find that the topography and conductivity can affect the SNMR response, which needs to be considered while interpreting SNMR data.

Monitoring variations in multimode surface topography

The recent development of optical measuring instruments has increased the use of surface topographic data for monitoring the quality of the engineered surface. Due to the complexities of modern industrial processes, however, surfaces of final products under the normal manufacturing process may have multiple modes, such that the surface consists of different topographic features from one in-control mode to another. In this case, existing monitoring approaches based on the single mode surface cannot characterise normal surfaces with multiple modes, and result in poor detection performance. In this article, a new approach for monitoring variations in multimode surface topography is presented. We propose a multimode surface prediction model, which characterises the generic behaviour of normal surfaces with multiple in-control modes. Moreover, we present a mode-specific surface monitoring approach that identifies topographic variations on the surfaces based on the similarity between probability density function (PDF) of residuals from observed and normal surfaces obtained through the prediction model. A novel probabilistic distance measure is introduced to effectively measure the similarity between a single residual PDF and a set of residual PDFs under the same mode. The effectiveness of the proposed approach is demonstrated through numerical simulation and real-life application of paper surface monitoring.

Comparative evaluation of the physical properties of membranes for periodontal regeneration: An In vitro Study

Introduction: Barrier membranes are the devices used in guided tissue regeneration procedures to promote the repopulation of the wound space by periodontal ligament cells. Commercially available membranes have been used widely for periodontal regeneration. The aim of the present study is to compare and evaluate the physical properties of membranes used for periodontal regeneration. Materials and Methods: The tensile strength and surface topography using scanning electron microscope were analysed of three commercially available membranes: chorion membrane, Healiguide™ membrane and PerioCol®-GTR membrane were analysed. Results: The tensile strength of the PerioCol®-GTR membrane was the highest, while that of the Chorion membrane was the least. Variations in the surface topography were observed in all three membranes groups. Conclusion: The study demonstrated variation in surface topography and tensile strength of the resorbable periodontal membranes, suggestive of differences in the time of resorption during regenerative periodontal procedures.

Hydrogeochemical Response of a Variably Saturated Sulfide‐Bearing Mine Waste‐Rock Pile to Precipitation: A Field‐Scale Study in the Discontinuous Permafrost Region of Northern Canada

AbstractGlobally, drainage from sulfide‐bearing waste‐rock piles, containing high concentrations of toxic metal(loid)s, can severely degrade surrounding ecosystems. Waste‐rock piles are typically deposited as unsaturated porous media. The complex physical and chemical heterogeneity of waste rock poses significant challenges to the evaluation of internal hydrological, (bio)geochemical, and mineralogical controls on the magnitude and duration of environmental impacts. An operational‐scale waste‐rock pile located in the discontinuous permafrost region of Northern Canada was well‐instrumented and monitored to examine hydrological processes (including precipitation, evaporation, and infiltration), hydrological and thermal responses to freeze‐thaw and dry‐wet cycles, and concentration‐discharge (cQ) relationships in drainage‐water quantity and quality. The net infiltration (subtraction of evaporation from precipitation) into the waste‐rock pile occurred from May to November, resulting in rainfall‐dominated recharge to pore water, surface seepage, and groundwater. Pronounced variations in water content and temperature in response to freeze‐thaw and dry‐wet cycles and variations in surface topography were observed in regions of the waste‐rock pile impacted by preferential flow pathways. In contrast, distinct variations in water content and temperature were not observed in regions of matrix‐dominated flow pathways. The cQ relationships show chemodynamically controlled dilution behavior for most dissolved constituents (e.g., SO4, Fe, Pb, Zn, Cu, Ca, Mn) in the drainage. Therefore, hydrological processes and (bio)geochemical and mineralogical reactions both play prominent roles in determining drainage‐water chemistry. This work presents an integrated approach to site‐specific monitoring and characterization to evaluate remediation and reclamation options for operational‐scale waste‐rock piles for long‐term ecosystem preservation.

Assessment of CryoSat-2 Baseline-D Height Product by GNSS and ICESat-2 in Lambert-Amery System, East Antarctica

CryoSat-2 repeatedly collects dense radar altimetry footprints covering high latitudes of the polar ice sheets for over ten years. The Baseline-D height product of CryoSat-2 was recently upgraded and released in 2019. Based on the internal or locally external evaluation of CryoSat-2 Baseline-D ice heights, we extended the validation both heterogeneously and spatially to accomplish a comprehensive assessment. First, reliable ice surface global navigation satellite system point solutions along the 36th Chinese National Antarctic Research Expedition traverse functioned as a height reference for comparison with the CryoSat-2 SAR synthetic aperture radar interferometric mode (SIN) data. Secondly, the Land Ice Along-Track Height product over Lambert–Amery system (LAS) from ice, cloud, and land elevation satellite 2 (ICESat-2), was also applied to validate CryoSat-2 SIN and low-resolution mode (LRM) data. As the results indicate, the SIN height accuracy is evaluated to be −1.68 m ± 2.35 m (slope < 0.65°) along the traverse and −0.96 ± 1.95 m (slope < 0.95° and roughness < 3 m) over the margin of LAS. The LRM height accuracy is evaluated to be −0.13 ± 0.46 m (slope < 0.1° & roughness < 1 m) over the interior of LAS. The standard deviation of the height differences degrades linearly against the limited growth of the terrain slope/roughness at the confidence level of 99%. It is worth noting that the spatially heterogeneous pattern of height differences is correlated with surface topography variations. This article should imply the potential to improve the estimation of mass balance and its uncertainty of polar ice sheets based on radar altimetry data.

Surface topography irregularities generated by broaching

Surface topography irregularities generated by broaching are analysed. Experimental tests were carried out on three workpiece materials: AISI 1045, Ti-6Al-4V, and Inconel 718, varying the cutting speed, rise per tooth, and rake angle. The experimental results combined with numerical simulation demonstrate that surface topography irregularities result from mechanical rather than thermal effects. Higher surface topography variations are obtained when the force magnitude increases, and when its direction is more perpendicular to the machined surface. Additionally, the Young's modulus of both the workpiece and tool materials plays a fundamental role in topography quality, reducing irregularities when the Young's modulus is increased.

Characterization of Surface Topography Variation in the Ultra-Precision Tool Servo-Based Diamond Cutting of 3D Microstructured Surfaces.

Previous models of the relative tool-work vibration are not generalized to represent the surface generation mechanism in the ultra-precision tool servo-based diamond cutting (UTSDC) of three-dimensional (3D) microstructured surfaces. This is due to the fact that the tool-work vibration in UTSDC is no longer a steady harmonic vibration with a constant amplitude but is influenced by the tool motion along the thrust direction. In this paper, dynamic modeling of the cutting system is presented for the characterization of surface topography variation in UTSDC of a microlens array considering the tool-work vibration as an underdamped vibration. The natural frequency and damping ratio of the cutting system are determined by the data-dependent systems (DDS) method. Based on the analysis of the surface profile and cutting force signals, it is found that the tool-work vibration is significantly enhanced in the cut-in process when the cutting speed increases. The simulation results show that the proposed dynamic model can well-determine root-mean-squares values of the surface primary profile and the dynamic force acting on the force sensor. The dynamic model provides insight into the formation of the surface topography variation in UTSDC of 3D microstructured surfaces, and the model might be applied in self-optimized machining systems in the future.

Fractal variation of three-dimensional surface topography during sliding wear under mixed elastohydrodynamic lubrication

The surface morphology variation of the friction pair during the wear process directly affects the local lubrication effect and contact strength, and this variation is difficult to quantify in mixed lubrication. In this study, a numerical simulation and characterization model method of sliding wear surface morphology evolution based on deterministic elastohydrodynamic lubrication (EHL) model and surface three-dimensional morphology fractal method is established. The effectiveness of the lubrication model is verified by the film thickness measurement, and the actual surface wear coefficient is obtained through the wear experiment. On this basis, the variation of surface morphology and fractal parameters in the sliding wear process is investigated, and the effect of contact load and sliding speed on surface lubrication characteristics and fractal parameters is analyzed. The results show: wear will cause the higher wave peaks on the ground surface to be gradually worn away and the fine structure of the surface is reduced, and the fractal dimension of the morphology is therefore reduced. In addition, the contact area ratio and contact load ratio, as well as the coefficient of friction and surface evolution under different loads and sliding speeds are consistent.

Roughness evolution of constrained surface based on crystal plasticity finite element model and coupled Eulerian-Lagrangian method

This paper focuses on the roughness evolution and surface topography variation of constrained surface, which is restricted by the mold or tool in the forming process. A crystal plasticity finite element model, which couples the microstructure of polycrystalline, the crystal plasticity constitutive model and the real surface topography of the material, is developed. How to use the real surface of the workpiece as the surface topography of the finite element model is proposed, in which number and location of peaks and valleys on the surface, are accurately captured in the constructed real surface model. The comparison shows that simulation predictions of both the deformed surface topography and the surface roughness agree reasonably well with experimental measurements at various press down ratio of mold. The influences from workpiece and mold on the roughness evolution of constrained surface are comprehensively analyzed. It can be seen clearly that roughness evolution of constrained surface is the combination result of both the surface flattening due to the mold restriction and the surface roughening due to the material inhomogeneity of the workpiece. The lubricant existing in the contact surface of the workpiece and mold should been paid much more attention in the roughness evolution analysis. The influence of the lubrication condition on the roughness evolution of constrained surface is analyzed by combining the CEL finite element method and compression experiments. In deformation stage II of the roughness evolution, the closed cavities begin to form on the surface. Lubricant in the closed cavities plays an important role in limiting the flattening behavior of the surface topography. This paper provides a deeper insight into the comprehensive understanding of the roughness evolution of constrained surface, which contributes to the surface roughness control of plastic deformation products considering the effects of the workpiece, mold and lubrication condition.

Characterization of Calcium Phosphate Spherical Particles in the Subretinal Pigment Epithelium–Basal Lamina Space in Aged Human Eyes

PurposeMicrometer-sized spherules formed of hydroxyapatite or whitlockite were identified within extracellular deposits that accumulate in the space between the basal lamina (BL) of retinal pigment epithelium (RPE) and the inner collagenous layer of Bruch’s membrane (sub-RPE–BL space). This investigation aimed to characterize the morphologic features, structure, and distribution of these spherules in aged human eyes with and without clinical indications of age-related macular degeneration (AMD).DesignExperimental study.ParticipantsFive human eyes with varying degrees of sub-RPE–BL deposits were obtained from the University College London Institute of Ophthalmology and Moorfield’s Eye Hospital Tissue Repository or the Advancing Sight Network. Two eyes were reported as having clinical indications of AMD (age, 76–87 years), whereas 3 were considered healthy (age, 69–91 years).MethodsCadaveric eyes with sub-RPE–BL deposits were embedded in paraffin wax and sectioned to a thickness of 4-10 μm. Spherules were identified and characterized using high-resolution scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy, and time-of-flight secondary ion mass spectroscopy.Main Outcome MeasuresHigh-resolution scanning electron micrographs of spherules, the size-frequency distribution of spherules including average diameter, and the distribution of particles across the central-peripheral axis. Elemental maps and time-of-flight secondary ion mass spectra also were obtained.ResultsThe precipitation of spherules is ubiquitous across the central, mid-peripheral, and far-peripheral axis in aged human eyes. No significant difference was found in the frequency of spherules along this axis. However, statistical analysis indicated that spherules exhibited significantly different sizes in these regions. In-depth analysis revealed that spherules in the sub-RPE–BL space of eyes with clinical signs of AMD were significantly larger (median diameter, 1.64 μm) than those in healthy aged eyes (median diameter, 1.16 μm). Finally, spherules showed great variation in surface topography and internal structure.ConclusionsThe precipitation of spherules in the sub-RPE–BL space is ubiquitous across the central–peripheral axis in aged human eyes. However, a marked difference exists in the size and frequency of spherules in eyes with clinical signs of AMD compared to those without, suggesting that the size and frequency of spherules may be associated with AMD.

An optimized finite difference method based on a polar coordinate system for regional-scale irregular topography

The finite difference method (FDM) is an important numerical approach for simulating the propagation of seismic waves, and some FDMs can be used to study the impact of the Earth’s curvature and topography over large distances. To efficiently model the effects of the Earth’s irregular topography on the propagation of seismic waves, here we optimize a previously proposed grid mesh method and develop a novel two-dimensional boundary-conforming FDM based on a curvilinear polar coordinate system. This method efficiently simulates the propagation of seismic waves in an arc-shaped model with large variations in surface topography. Our method was benchmarked against other reported methods using several global-scale models. The consistency of the results confirms the validity of our proposed optimization strategy. Furthermore, our findings indicate that the proposed optimization strategy improves computational efficiency.

Tensile Behavior of Geometrically Irregular Bagasse Fiber

In the present work, an investigation on the surface topography and geometry variation of bagasse fibers was correlated with their mechanical properties via image analysis. The fibers were tested under a universal tensile testing machine and the diameter of the fibers was calculated using images obtained in a digital microscope. Furthermore, surface characterization and quantification were also performed using images obtained via SEM. The results showed that the surface roughness of alkali-treated bagasse fiber increased compared to that of the untreated one. Moreover, it was observed that the diameter variation of bagasse fiber along its length and among different fibers is not only variable but also unpredictable. The tensile test results revealed that bagasse fibers showed lower stress at a rupture with considerable scatter. It can be inferred that the synergistic effect of thick bagasse fiber, bagasse fiber diameter variations along its length and among fibers, and the fiber fracture mechanism establishes a local condition for fracture and resulted in such variations in tensile properties. Finally, the results clearly showed that the two-parameter Weibull fit the experimental data fairly well (R2=0.97). The Weibull modulus (m) was found to be 1.7, indicating that the strength distribution is high.

Surface Topography of the Metal surface in Robot Polishing under Control Force

Polishing is an important finishing process in the field of manufacturing, which enhances product quality and increases its life span. Compared with manual polishing, robotics polishing has advantages in terms of cost and productivity. This paper presents a new study on the surface topography of metal workpiece in the robotic polishing test. Various workpieces with different surface roughness were polished with the industrial robot under similar polishing parameters, and the variation of surface topography with polishing was studied utilizing microscopic scanning.

Locating Rockfalls Using Inter‐Station Ratios of Seismic Energy at Dolomieu Crater, Piton de la Fournaise Volcano

AbstractRockfalls generate seismic signals that can be used to detect and monitor rockfall activity. Event locations can be estimated on the basis of arrival times, amplitudes, or polarization of these seismic signals. However, surface topography variations can significantly influence seismic wave propagation and hence compromise results. Here, we specifically use the signature of topography on the seismic signal to better constrain the source location. Seismic impulse responses are predicted using Spectral Element based simulation of three‐dimensional wave propagation in realistic geological media. Subsequently, rockfalls are located by minimizing the misfit between simulated and observed inter‐station energy ratios. The method is tested on rockfalls at Dolomieu crater, Piton de la Fournaise volcano, Reunion Island. Both single boulder impacts and distributed granular flows are successfully located, tracking the complete rockfall trajectories by analyzing the signals in sliding time windows. Results from the highest frequency band (here 13–17 Hz) yield the best spatial resolution, making it possible to distinguish detachment positions less than 100 m apart. By taking into account surface topography, both vertical and horizontal signal components can be used. Limitations and the noise robustness of the location method are assessed using synthetic signals. Precise representation of the topography controls the location resolution, which is not significantly affected by the assumed impact direction. Tests on the network geometry reveal best resolution when the seismometers triangulate the source. We conclude that this method can improve the monitoring of rockfall activity in real time once a simulated database for the region of interest is created.