Variations In Surface Topography Research Articles

Multiscale Analysis of Surface Topography for Engineering Applications in the Casting Industry.

This paper presents the results of studies aimed at assessing the impact of the molding process on the variability of surface irregularities of casting models. This research was conducted using a selected multiscale method, i.e., wavelet transformation, in both discrete and continuous perspective. The test samples were made both based on traditional methods of manufacturing casting models, i.e., machining of aluminum and wood, as well as using three additive technologies. The impact of the forming process on the variability of the topography of the produced models was evaluated. This research comprehensively relates to the assessment of the applicability of additive technologies, which are increasingly used in various industrial areas, as well as the impact of the process on surface topography in relation to scale. The statistical assessment based on the ANOVA analysis demonstrated that it is possible to distinguish between the surfaces before and after a specific number of forming cycles. Studies have shown that the impact of the forming process is relatively small, mainly affecting the long-term irregularity components, and there are no functional dependencies in terms of the impact of the forming process on the variation in surface topography in relation to the manufacturing method or its parameters.

The effect of semi-curing on neat resin mode I fracture properties

The sensitivity of fracture toughness to the cure path of a high-performance hot infusion epoxy resin (EP2410) is assessed in this study through single-edge notch bend testing of neat resin specimens. The specimens were prepared using a two-stage semi-curing process. In the initial stage, the partial degree of cure and the semi-cure temperature were varied. In the second stage, samples were heated to 180 °C for a secondary post-cure. These samples were compared to two baseline samples produced using the manufacturer's recommended cure cycle of 180 °C, and a modified isothermal cure at a lower cure temperature of 140 °C. The results show that the semi-curing path has no statistically significant influence on the mode I fracture toughness of the material studied here. Sample similarity was confirmed through SEM examination of the fracture surface, which showed minimal variation in surface topography. These findings open new possibilities to use this type of material for novel manufacturing processes involving semi-curing steps.

A novel stress sensor enables accurate estimation of micro-scale tissue mechanics in quantitative micro-elastography.

Quantitative micro-elastography (QME) is a compression-based optical coherence elastography technique enabling the estimation of tissue mechanical properties on the micro-scale. QME utilizes a compliant layer as an optical stress sensor, placed between an imaging window and tissue, providing quantitative estimation of elasticity. However, the implementation of the layer is challenging and introduces unpredictable friction conditions at the contact boundaries, deteriorating the accuracy and reliability of elasticity estimation. This has largely limited the use of QME to ex vivo studies and is a barrier to clinical translation. In this work, we present a novel implementation by affixing the stress sensing layer to the imaging window and optimizing the layer thickness, enhancing the practical use of QME for in vivo applications by eliminating the requirement for manual placement of the layer, and significantly reducing variations in the friction conditions, leading to substantial improvement in the accuracy and repeatability of elasticity estimation. We performed a systematic validation of the integrated layer, demonstrating >30% improvement in sensitivity and the ability to provide mechanical contrast in a mechanically heterogeneous phantom. In addition, we demonstrate the ability to obtain accurate estimation of elasticity (<6% error compared to <14% achieved using existing QME) in homogeneous phantoms with mechanical properties ranging from 40 to 130 kPa. Furthermore, we show the integrated layer to be more robust, exhibiting increased temporal stability, as well as improved conformity to variations in sample surface topography, allowing for accurate estimation of elasticity over acquisition times 3× longer than current methods. Finally, when applied to ex vivo human breast tissue, we demonstrate the ability to distinguish between healthy and diseased tissue features, such as stroma and cancer, confirmed by co-registered histology, showcasing the potential for routine use in biomedical applications.

Sustainable concrete production: Mechanical and durability behaviour of slag-based geopolymer containing recycled geopolymer aggregate

Geopolymer binders, synthesized by activating aluminous and silicate-rich materials with alkalis, are attracting great interest as an environmentally friendly building material to replace cement due to their low CO2 emissions and the possibility of disposing of industrial wastes. Intensive research on geopolymer binders and the prospect of their future widespread use have raised questions about end-of-life strategies for geopolymer concrete (GPC). In this study, the durability and mechanical properties of new geopolymer concrete (GRAC) produced from aggregate derived from one-part slag-based GPC subjected to ambient curing were investigated. In addition to the properties of recycled geopolymer aggregates (RGAs) such as ASR reactivity, water absorption rate, organic matter content, specific gravity, the effects of RGA size and amount on mechanical strength, SEM analysis, surface topography and length variation of new GRAC produced by adding different proportions of fine and coarse RGAs (30 %, 60 % and 100 %) were investigated. Consequently, it was observed that GRAC exhibited a mechanical strength comparable to that of GPC produced with natural aggregate, while the void content, water absorption rate, surface pores and microcracks of GRAC increased with the increase in RGA content. In addition, the resistance of GRAC to environmental degradation (acid, sulfate, salt and water effect) decreased with the increase in porosity. The high water absorption rate, porous structure and weak interface region (ITZ) of RGAs make GRAC produced with these aggregates more sensitive to external aggressive chemicals.

Generalizing electroosmotic-flow predictions over charge-modulated periodic topographies: tuneable far-field effects

The classical Helmholtz–Smoluchowski (HS) model of electroosmosis holds for homogeneously charged interfaces in contact with a fluid layer bearing an equal and opposite net charge. However, inhomogeneities in the surface charge and topography are inevitable, either as practical materials and fabrication artefacts, or at times as deliberately introduced modulations for flow control. In an effort to arrive at an analytically tractable theoretical framework for addressing the underlying electro-mechanical coupling, here, we generalize the traditional HS theory to an extent where both the surface charge and topographies may bear arbitrary and independent periodic forms. Using a spectral-asymptotic approach, we further arrive at closed-form expressions for describing the resulting electroosmotic pumping for topographic features with small characteristic amplitude to pattern period ratio, as relevant for most practical scenarios. We subsequently execute full-scale numerical simulations without any restrictions on the surface charge and topography variations to assess the efficacy of the theoretical framework. The corresponding test beds include distinctive signature patterns – for example, a square-wave surface charge distribution on trapezoidal pit topographies. Our results reveal that the charge–topography interplay induces an anisotropic flow drift, deviating from the classical HS paradigm. This, in turn, provides new quantitative insights into highly selective electroosmotic flow control via judicious design of the charge and topographical patterns, resulting in controllable accentuation, attenuation, nullification, deflection and even complete reversal of the flow. Our analysis further establishes a provision of estimating the zeta potentials of naturally ‘contaminated’ surfaces, as well as explaining the electrophoresis of large inhomogeneous particles; a paradigm that remained to be explored thus far.

Decoding Excimer Formation in Covalent-Organic Frameworks Induced by Morphology and Ring Torsion.

A thorough and quantitative understanding of the fate of excitons in covalent-organic frameworks (COFs) after photoexcitation is essential for their augmented optoelectronic and photocatalytic applications via precise structure tuning. The synthesis of a library of COFs having identical chemical backbone with impeded conjugation, but varied morphology and surface topography to study the effect of these physical properties on the photophysics of the materials is herein reported. The variation of crystallite size and surface topography substantified different aggregation pattern in the COFs, which leads to disparities in their photoexcitation and relaxation properties. Depending on aggregation, an inverse correlation between bulk luminescence decay time and exciton binding energy of the materials is perceived. Further transient absorption spectroscopic analysis confirms the presence of highly localized, immobile, Frenkel excitons (of diameter 0.3-0.5nm) via an absence of annihilation at high density, most likely induced by structural torsion of the COF skeletons, which in turn preferentially relaxes via long-lived (nanosecond to microsecond) excimer formation (in femtosecond scale) over direct emission. These insights underpin the importance of structural and topological design of COFs for their targeted use in photocatalysis.

Space-weathering induced changes in hydrated silicates: A multi-scale study combining visible/infrared spectroscopy and electron microscopy

Investigating the effects of space-weathering on primitive bodies is paramount in assessing their composition and understanding their history. For this purpose, we conducted 40 keV He and Ar ion-implantation experiments on terrestrial phyllosilicates, the main components of primitive C-class asteroids: two serpentines, and one saponite. We emulated the effects of the solar wind component of space weathering on hydrated surfaces over timescales of 1E3–4 years in the inner solar system. Spectral changes (from 0.35 to 30 μm in wavelength), surface topography variations, and elemental and morphological changes were investigated. In the visible range, we saw darkening for all samples, accompanied by reddening for the serpentine samples and blueing for the saponite. Spectroscopic features such as the silicate stretching and bending modes at 10 and 20 μm respectively, as well as the (M)-OH bending mode at 16 μm, exhibited a peak shift towards longer wavelength (red-shift), band area decrease, and band widening. The surface of Ar-implanted samples appeared polished, while no difference was noticeable for He-implanted samples. Morphological changes in the ion-implanted layers of our samples include abundant vesiculation and lattice amorphization. Mg and O appear to be particularly mobile upon ion implantation. In particular, dehydroxylation was observed for all samples. Changes observed for spectroscopic features do not correlate systematically with variations of the Mg/Fe ratio. They do correlate with oxygen loss via dehydroxylation and crystal lattice disordering and amorphization. Spectral changes in the visible range and for 10 and 20 μm features appear to be mainly due to crystal amorphization. Variation of the hydration feature at 16 μm correlates with both dehydroxylation and lattice amorphization. Compositional variations affect the hydration feature at 2.7 μm more consistently. The effects detected upon ion implantation on the samples in this work support the identification of spectral trends from the remote-sensing data of primitive bodies Ryugu and Bennu as changes induced by space-weathering. Findings are also compatible with laboratory analysis on returned weathered grains from Ryugu.

Improved Orthorectification and Empirical Reduction of Topographic Effects in Monostatic Mini-RF S-band Observations of the Moon

The Miniature Radio Frequency instrument (Mini-RF) on the Lunar Reconnaissance Orbiter obtained widespread synthetic aperture radar observations of the Moon in the S band (12.6 cm), including nearly complete coverage at both lunar poles. The currently archived monostatic data have spatial offsets from the lunar reference frame, making them more difficult to compare to other data sets. To address this issue, we have developed a new algorithm for spatially controlling the Mini-RF S-band monostatic data set and orthorectifying these data onto lunar topography. Additionally, as the influence of incidence angle changes on radar observations is well known, we describe an empirical approach to account for variations in observation geometry and surface topography. Individual radar swaths and mosaics produced using this method more clearly show the variability in scattering behavior due to changes in lunar regolith properties and suppress some of the behavior arising from these topographic effects alone. Once these terrain effects are taken into account, we find that areas of permanent shadow at both poles have a higher median radar reflectivity than nonpermanently shadowed regions, but the polarization behavior of shadowed versus unshadowed areas is largely similar. The higher radar reflectivity in permanent shadow is likely the result of physical or compositional differences in these unique environments, though the precise cause remains uncertain. The results here illustrate how reducing the influence of topography and geometry effects in Mini-RF radar data may enable better characterization of lunar geologic units, regolith structure, and potential areas hosting volatile deposits at the lunar poles.

Effects of cyclic fatigue loads on surface topography evolution and hydro-mechanical properties in natural and artificial fracture

This work investigated permeability evolution for fluid flow through natural fractures and artificial fractures in granite and the evolution of failure surface under cyclic fatigue loads condition. We revealed and compared a clear distinction between two types of fracture surfaces before and after the test, and analyzed the evolution of fracture surface roughness and other parameters which can characterize their topography feature, as well as the relationship between fracture surface topography and permeability. The studies indicated that artificial fractures show the higher roughness and subtler variations of surface topography than those of natural fractures, however, the surface topography of natural fractures was more susceptible to cyclic fatigue loads. The initial permeability and average permeability of nature fractures were both higher than those of artificial fractures during the stress-seepage coupling test and the permeability of artificially fracture was more sensitive to normal stress changes. Moreover, the experimental results were in line with theoretical predictions and the research results can provide reference for preventing the failure of rock engineering.

Characteristics of high-power impulse magnetron sputtering (HiPIMS) deposited nanocomposite-TiAlSiN coating under variable pulse frequencies

In the present study, nanocomposite-TiAlSiN coatings were deposited on WC-Co blocks using HiPIMS technology by varying pulse frequency. Its immediate effect on V–I signature and subsequent results on coating characteristics was critically investigated. Both substrate and target were negatively biased in pulsed mode but the voltage pulses on substrate was set with an offset of 40 μs, with respect to those on targets to avoid gas ion entrapment within coating. Variation of elemental composition, cross-sectional morphology, surface topography, hardness, and adhesion strength of the coating deposited under different pulsed frequencies, were analyzed in depth. TiAlSiN at the highest frequency, showed significant improvements in hardness and scratch resistance. A significant rise in Lc3 was recorded to be from 137.5 to 158.5 N when the pulse frequency was increased from 1 to 4 kHz. On the other hand, the peak target current was found to decrease from 340 A to 106 A. XRD spectra of TiAlSiN showed a peak shift from AlN (200) to TiAlN (200). Higher deposition rates were achieved with higher frequency but a compromise on surface smoothness, which was measured (Sa) with an increase from 9.42 to 14.32 nm.

Numerical Example to Estimate Groundwater Level Changes using Time-lapse Microgravity Data

The study using time-lapse microgravity (TLM) data can be helpfull to understand near surface variation caused by hidrological variation. Shallow groundwater variation can be highly correlated with density variation as time-lapse microgravity source, because the changes are very close to the surface. For several days (or weeks or months), we can observe density variation in the near surface caused by the changes of water saturated zones. The time-lapse of density variation for several days can be simplified as groundwater table changes. The purpose of this work is to study time-lapse microgravity application for groundwater level estimation. Using numerical example, we utilize lateral variation of time-lapse microgravity signal and also surface topography. In order to do the estimation groundwater level for second TLM survey, we need the groundwater level data from first survey (and vice versa). After numerical example, we applied the algorithm in the study area of (5 × 5) km square in the Blora regency. The shallow groundwater level (0 to 14 meters below the surface) are observed after the second (2016) microgravity survey. From this work, we constrained the model using second groundwater level data. After iterative calculation of using TLM anomaly (value in the range of -80 to +80 microGal) with surface topography variation (in the range 90 to 230 meters), we get the estimation the first (2014) groundwater level variation in the range of -7 to 7 meters from the second (2016) groundwater level data.

Spatial randomness-based anomaly detection approach for monitoring local variations in multimode surface topography

Spatial randomness-based anomaly detection approach for monitoring local variations in multimode surface topography

Local variability of a taiga snow cover due to vegetation and microtopography

ABSTRACT The taiga snow cover accumulates in relatively stable and windless weather. This should produce a uniform snow cover with continuous, laterally homogeneous stratigraphy and snow properties when the snow is deposited on a level, smooth substrate. However, such substrates are rare, and local variations in vegetation and ground surface topography alter the structure of the snow cover and produce irregular snow layers. In this study, we investigated the effects of vegetation, microtopography, and microclimatic variability on the taiga snow near Fairbanks, Alaska. Through the winter of 2019–2020, in situ measurements were made at three locations with distinctly different local microtopographic features and radically different (but typical) vegetation. One site was an open grassy field, the second a mature spruce forest, and the third a birch forest located on thermokarst terrain with steep microrelief where ice wedges had degraded. Widely different canopy interception processes proved to have the strongest impact on the resulting snow cover heterogeneity by altering the initial deposition, with surface microtopography having the second strongest influence through postdepositional processes. In this article, we suggest a conceptual framework for understanding and modeling taiga snow variability in terms of the vegetation and microtopography that created it.

The Causes and Effects of Preannealed Radiative Property Variations Across Full‐Hard Advanced High‐Strength Steel Coils

This study investigates the connection between surface topography and radiative property variations across full‐hard (unannealed and cold‐rolled) advanced high‐strength steel (AHSS) coils. Directional–hemispherical reflectivities of samples extracted from various locations on a full‐hard DP‐780 coil are measured using a Fourier transform infrared spectroscopy spectrometer at wavelengths between 0.5 and 20 μm. Surface topography analysis is performed using optical profilometry, optical microscopy, and scanning electron microscopy. Surface height profiles are generated using 3D depth mapping of optical images. The surface profiles are then used in a geometric optical approximation model, which correlates the radiative properties to surface topography variations. Significant differences in radiative properties and surface topography are observed along the length and width of the coil. These variations in radiative properties may explain the temperature excursions that cause nonuniformities in mechanical properties observed across AHSS coils produced on continuous galvanizing lines in the industry.

Water wettability alternation of CO2-water-shale system due to nanoparticles: Implications for CO2 geo-storage

The wettability of rocks is closely related to the CO2 geo-storage (CGS) security after CO2 injection into the reservoir. Nanofluids can be used to efficaciously alter the wettability of the CO2-water-rock system toward an advantageous state (water-wet) for CGS. In this study, we investigated the potential of SiO2 and Al2O3 nanofluids at different aging time and concentrations to retain the wettability reversal of CO2-exposed shale from the Sichuan Basin after supercritical carbon dioxide (ScCO2) exposure. Fourier Transform Infrared Spectrometer and field emission scanning electron microscopy tests were performed to evaluate the variations of functional groups and surface topography of shale. Results indicated that both nanoparticles efficiently retain the wettability reversal of shale after a period of ScCO2 treatment, which is conducive to structural trapping in the CGS project. The efficiency was improved by increasing the nanofluid aging time and concentrations, while beyond a certain value, the contact angle value changed trivially. Quasi-homogeneously distributed on the shale surface in ScCO2 may contribute to the wettability alteration of shale in ScCO2, whereas there are still removals of nanoparticles in some sites. The variations of functional groups suggest that the existence of nanoparticles may mildly expedite the CO2 mineralization, signifying the change of wetting behavior of shale in ScCO2 depends on the wettability of nanoparticles, and the nanofluids treatment may exert a positive influence on mineral trapping in the CGS project. The findings in this research provide an important basis for raising the CO2 geological storage security and potential via nanofluids.

A Spatial Downscaling Method for Deriving High-Resolution Downward Shortwave Radiation Data Under All-Sky Conditions

Downward shortwave radiation (DSR) is an essential parameter in land surface energy budget. However, current DSR products are mainly generated at coarse-resolution scales (more than 5 km) and fail to accurately depict DSR distribution over different topographic and land cover conditions. Meanwhile, the existence of frequent cloud cover constrains the high-resolution DSR estimation. To overcome the above issues, a novel spatial downscaling method for high-resolution DSR estimation was proposed in this study by incorporating coarse-resolution Meteosat Second Generation (MSG) DSR product and Landsat-8 observations. Through decomposing the downscaling scheme into three separate models: fully cloudy, partial cloudy, and cloud-free, the 3 km MSG DSR data was spatially downscaled to 30 m scale under all-sky conditions, based on the assumption of scale-invariant of the models established at 3 km scale. An empirical model for DSR estimation under cloud cover condition was constructed between the top of atmosphere radiance from Landsat-8 and MSG DSR. The downscaled results showed reasonable DSR values under different cloud cover conditions and the spatial heterogeneity of the downscaled DSR was also well depicted with the variation of surface topography. Meanwhile, the validation with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-situ</i> measurements also revealed the significant improvement in terms of the coefficient of determination (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) (from 0.53 to 0.79) and the root mean squared error (RMSE) (from 198.5 to 140.41 W/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). In general, the proposed downscaling method in this study show good potential for high-resolution DSR estimation without regard to the atmospheric information required in traditional DSR estimation under all-sky condition.

Three dimensional (3D) printing in Orthopaedics: Scope of application and future perspectives

Three dimensional (3D) printing also known as additive manufacturing has the potential to change the paradigm of Orthopaedic practice. Modern times have witnessed exponential growth in 3D-printing technology as well as its uses. A wide spectrum of printers are now available, ranging from the desktop printer to high end manufacturing units. The ability to use a plethora of materials and create almost limitless geometric shapes with varying surface topography makes this method of production highly appealing. Certain inherent advantages include easy customizability, small production runs, less wastage of material, smaller footprint. Challenges such as lack of data, absence of established government regulations and cost considerations remain, but one can expect these to be overcome as the economy of scale plays out and the medical fraternity becomes more accommodating of the new technology. Keywords: Three dimensional printing, Recent Advances, Arthroplasty, Spine, Tumor Implants

Quantifying the Influence of Surface Texture and Shape on Structure from Motion 3D Reconstructions

In general, optical methods for geometrical measurements are influenced by the surface properties of the examined object. In Structure from Motion (SfM), local variations in surface color or topography are necessary for detecting feature points for point-cloud triangulation. Thus, the level of contrast or texture is important for an accurate reconstruction. However, quantitative studies of the influence of surface texture on geometrical reconstruction are largely missing. This study tries to remedy that by investigating the influence of object texture levels on reconstruction accuracy using a set of reference artifacts. The artifacts are designed with well-defined surface geometries, and quantitative metrics are introduced to evaluate the lateral resolution, vertical geometric variation, and spatial-frequency information of the reconstructions. The influence of texture level is compared to variations in capturing range. For the SfM measurements, the ContextCapture software solution and a 50 Mpx DSLR camera are used. The findings are compared to results using calibrated optical microscopes. The results show that the proposed pipeline can be used for investigating the influence of texture on SfM reconstructions. The introduced metrics allow for a quantitative comparison of the reconstructions at varying texture levels and ranges. Both range and texture level are seen to affect the reconstructed geometries although in different ways. While an increase in range at a fixed focal length reduces the spatial resolution, an insufficient texture level causes an increased noise level and may introduce errors in the reconstruction. The artifacts are designed to be easily replicable, and by providing a step-by-step procedure of our testing and comparison methodology, we hope that other researchers will make use of the proposed testing pipeline.

Negative Pressure Wound Therapy in the Head and Neck: A Summary of Uses and Application Techniques.

Negative pressure wound therapy (NPWT) has had an expanded role in the management of complex wounds including its increasing use for complex wounds in the head and neck region. Challenges for use in the head and neck region include variations in surface topography and the proximity of sensitive mouth, nose, ear, eye, and tracheal openings. Despite these challenges, NPWT has been used in the head and neck immediately following free flap surgery, to prepare wounds for skin grafting or local flaps, to treat orocutaneous and pharyngocutaneous fistulas, to treat necrotizing and deep neck space infections, to temporize and palliate, and to treat chronic wounds with exposed bone and hardware among others. This review demonstrates the proven track record of successful uses of NPWT in the aforementioned scenarios, provides suggestions to improve efficacy, as well as an algorithm for use in certain clinical situations.

Change in surface characteristics and permeability of human enamel after subjecting to radiation therapy.

Radiation-related caries is a complex destructive lesion leading to uncompromising damage of enamel and dentin in patients suffering from head and neck cancer managed with radiotherapy. The purpose of this study was to evaluate the changes in the permeability of enamel and to assess the morphological and chemical changes of teeth surface subjected to 6 MV photon beam irradiation. For this in vitro study, coronal portion of 20 premolars were sectioned mesiodistally into halves and then grouped into two. Samples in group 1 (control) were not subjected to cycles of irradiation and those in group 2 (experimental) were subjected to a cumulative uniform radiation dose of 70 Gray fractioned in 35 fractions with 6 MV photons. The silver nitrate penetration method was used to assess the change in permeability of enamel. The variations in surface topography and mineral content were assessed using scanning electron microscopy with energy dispersive X-ray analysis. Dye penetration scores of surface texture changes were compared between the two groups utilizing the Chi-square test. The change in the elemental levels between enamel surfaces of the two groups was compared using an independent t-test. The application of 6 MV photon radiation did not change enamel permeability and surface topography. However, a noteworthy reduction in the carbon content (P = 0.002) was observed in teeth subjected to irradiation. Though radiation exposure did not alter the enamel permeability and surface topography, it had caused significant chemical compositional changes. Carbon content was significantly reduced in irradiated enamel samples.