Individual Surface Features Research Articles

Selective Surface Feature Electropolishing of Additively Manufactured 316L Using Pulse Electrochemistry

Electrochemical finishing of metallic surfaces is a scalable, relatively cost-effective technique that is also versatile. One of the main detractions is that the current distribution is uneven and unspecific, often leading to a lack of shape retention and, if it goes too far, inducing corrosion. Pulsing the electrical input creates an unsteady state during electropolishing, controlling the current distribution across the part. The pulse wave prevention of general non-uniform current distribution across the entire geometry instead produces local non-uniformities in the current distribution at given surface features. Many pulse electropolishing parameters can be varied to target individual surface features, including the electrolyte, pulse height, pulse width (equally and unequally distributed), time of polishing as well as the overall waveform.Additive manufacturing (AM) can produce unique, complex structures rapidly. The fast local melting of metal AM parts cool quickly due to the small area, causing unique microstructures, pores, and larger surface roughness compared to cast. AM microstructures change mechanical and chemical properties, such as strength and corrosion, compared to traditionally manufactured parts. Variations in build parameters and composition creates a complicated, feature dependent, corrosion response. By polishing the surface, some of the features, namely the corrosion resistance, wear, and aesthetics can be standardized and enhanced.In this work, we explore the underlying electrochemistry that governs pulse electropolishing. We show that controlling the electrolyte with environmentally benign chemicals ultimately influences the part dimensions that can be polished, the ability to polish, and the propensity to corrode. The pulse height, pulse width (Fig. 1), and total charge passed have an impact on different surface feature removal. We will demonstrate impact of the pulse parameters on the polishing of additively manufactured stainless steel. We go beyond simple planar geometry and apply our understanding to larger scale complex geometry parts, while maintaining near-net shape and minimizing mass loss. Figure 1

Chain length dependence of ZnO nanofiller–polystyrene blend coating nanofilm: Morphology, surface mechanics, photochemistry, and chain packing

Based on that chain packing which is associated with the number of entanglements per chain and thereby chain length is an influential factor closely related to the properties of polymeric coating film, the nanothin film of zinc oxide (ZnO) nanofiller–incorporated polystyrene (PS) coated on Si substrate important to electronic packaging for protecting electronic material surface is fabricated with different PS molecular weights primarily for heat–resistant coating. Synergistically, through directly–measurable film characteristics obtained using atomic force microscopy (AFM) and spectroscopy (AFS) in conjunction with Raman spectroscopy (RS), the internal structures of the films are evaluated which helps indicate the corresponding film properties tested afterwards. Considering mechanical responses of individual nanoscale surface features together with surface morphology, the optimal PS–ZnO film is pointed out which indicates improved resistance to thermal dewetting compared to pure PS films while providing sub–nanometer roughness and the highest contact area of relatively low–surface–energy sites. Correlated with Raman analysis, chain packing structure encouraging multiple amplification of incident light is ascribed to the films made of the optimal chain length which indicates and describes the observed enhancement of photocatalytic self–cleaning. This study not only contributes to the development of PS–ZnO composite for multi–function coating but also to the design of structure and inspection of nanoparticle–reinforced polymer thin films.

Insight into replication effectiveness of laser-textured micro and nanoscale morphology by injection molding

Abstract Detailed analysis and characterization of injection-molded polypropylene (PP) specimens produced with laser-textured molds has been performed. Ultrashort pulsed laser surface structuring was exploited to produce sub-micrometric surface features on injection molds over areas of 2400 mm2, including two-dimensional hole and cone arrays, and ridges parallel and perpendicular to the injection direction. Replication effectiveness was evaluated in terms of surface roughness parameters, Filling Volume Fraction (FVF) and Power Spectral Density (PSD), after which detailed comparison of the topography in the same region on plastic samples and molds was performed. A scatterometry setup was employed based on optical diffraction of a probe laser beam to assess replication fidelity over the entire surface of each PP sample with a measurement technique suitable for optimization and quality control in an industrial production environment. Of the tested surface morphologies, greatest replication effectiveness was achieved with LIPSS oriented parallel to the injection direction, where the arithmetic mean height of plastic samples (Sa = 37 ± 4 nm) was 97 % of the corresponding value of the mold (Sa = 38 ± 6 nm), while the average FVF was 86 ± 9 % and the PSD indicated ripple-like features with a spacing of λ ≃ 0.9 μm. Direct comparison of the topography in selected regions highlighted local variability in the transfer effectiveness of individual surface features. The investigation demonstrated that micro and nanoscale morphology can effectively be transferred via injection molding over large areas relevant to industrial applications, while careful attention must be paid to the size and nature of defects in relation to the specific functional surface under consideration.

Nonverbal category knowledge limits the amount of information encoded in object representations: EEG evidence from 12-month-old infants.

To what extent does language shape how we think about the world? Studies suggest that linguistic symbols expressing conceptual categories (‘apple’, ‘squirrel’) make us focus on categorical information (e.g. that you saw a squirrel) and disregard individual information (e.g. whether that squirrel had a long or short tail). Across two experiments with preverbal infants, we demonstrated that it is not language but nonverbal category knowledge that determines what information is packed into object representations. Twelve-month-olds (N = 48) participated in an electroencephalography (EEG) change-detection task involving objects undergoing a brief occlusion. When viewing objects from unfamiliar categories, infants detected both across- and within-category changes, as evidenced by their negative central wave (Nc) event-related potential. Conversely, when viewing objects from familiar categories, they did not respond to within-category changes, which indicates that nonverbal category knowledge interfered with the representation of individual surface features necessary to detect such changes. Furthermore, distinct patterns of γ and α oscillations between familiar and unfamiliar categories were evident before and during occlusion, suggesting that categorization had an influence on the format of recruited object representations. Thus, we show that nonverbal category knowledge has rapid and enduring effects on object representation and discuss their functional significance for generic knowledge acquisition in the absence of language.

Geometrical model for calculating the effect of surface morphology on total x-ray output of medical x-ray tubes.

PurposeCorrelation of characteristic surface appearance and surface roughness with measured air kerma (kinetic energy released in air) reduction of tungsten‐rhenium (WRe) stationary anode surfaces.MethodsA stationary anode test system was developed and used to alter nine initially ground sample surfaces through thermal cycling at high temperatures. A geometrical model based on high resolution surface data was implemented to correlate the measured reduction of the air kerma rate with the changing surface appearance of the samples. In addition to the nine thermally cycled samples, three samples received synthetic surface structuring to prove the applicability of the model to nonconventional surface alterations. Representative surface data and surface roughness values were acquired by laser scanning confocal microscopy.ResultsAfter thermal cycling in the stationary anode test system, the samples showed surface features comparable to rotating anodes after long‐time operation. The established model enables the appearance of characteristic surface features like crack networks, pitting, and local melting to be linked to the local x‐ray output at 100 kV tube voltage ,10° anode take off angle and 2 mm of added Al filtration. The results from the conducted air kerma measurements were compared to the predicted total x‐ray output reduction from the geometrical model and show, on average, less than 10 % error within the 12 tested samples. In certain boundaries, the calculated surface roughness Ra showed a linear correlation with the measured air kerma reduction when samples were having comparable damaging characteristics and similar operation parameters. The orientation of the surface features had a strong impact on the measured air kerma rate which was shown by testing synthetically structured surfaces.ConclusionsThe geometrical model used herein considers and describes the effect of individual surface features on the x‐ray output. In close boundaries arithmetic surface roughness Ra was found to be a useful characteristic value on estimating the effect of surface damage on total x‐ray output.

Image Fusion of SAR and Optical Images for Identifying Antarctic Ice Features

Remote sensing data plays an important role in extracting thematic information from various sensors having different spectral, spatial and temporal resolutions. The present study aims at fusion of Radar Imaging Satellite-1 Fine Resolution Stripmap-1 and ResourceSAT-2 Linear Imaging Self Scanning Scanner-4 (LISS-4) images over Indian Antarctic Research Station Maitri and its surroundings to generate a better product which contains the characteristics of both the spectral information from LISS-4 and the spatial details of SAR. Different pixel-based fusion techniques such as Brovey Transform, Principal Component Analysis (PCA), Intensity Hue Saturation and Wavelet Principal Component Analysis (W-PCA) have been used in the present study. These image fusion techniques have been applied for the whole scene as well as for individual surface features like melt ponds, crevasses, freshwater lake, blue ice, oasis and lake ice for better discrimination of features. Quality assessment is performed by evaluating the performance of these algorithms using visual, spatial (High Pass Correlation Coefficient and Entropy) and spectral (Root Mean Square Error, Correlation Coefficient, ERGAS and Universal Quality Index) parameters. It is found that the identification of certain features such as crevasses, blue ice, melt ponds and lake ice has been improved with fused images compared to the original multi-spectral and SAR images. PCA and W-PCA fusion techniques offer better performance as compared to the rest of the techniques.

The albedo of Mars: Six Mars years of observations from Pancam on the Mars Exploration Rovers and comparisons to MOC, CTX and HiRISE

The Mars Exploration Rovers (MER) Spirit and Opportunity have systematically used their Panoramic Camera (Pancam) instruments to estimate the Lambert albedo of the surface across their traverses in Gusev crater and Meridiani Planum. The 360˚ “albedo pan” observations acquired with Pancam's broadband (739 ± 338 nm) L1 filter allow for quantitative estimates of the overall surface albedo and measurements of individual surface features. As of November 2016, over nearly six Mars years of the MER mission, Spirit acquired 20 albedo pans (over 7,730 m of traverse distance) and Opportunity acquired 117 albedo pans (over 42,368 m of traverse distance). For Spirit, this comprises the rover's complete dataset. The ranges of Pancam-derived albedos at Gusev crater (0.14–0.24) and at Meridiani Planum (0.11–0.22, with one anomalously high measurement of 0.27 during the July 2007 global dust storm) are consistent with large-scale albedos of the sites as previously determined by the Viking Orbiter Infrared Thermal Mapper (IRTM), Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES), MGS Mars Orbiter Camera (MOC), Mars Odyssey Thermal Emission Imaging System (THEMIS), Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) and MRO Mars Color Imager (MARCI) instruments. Through comparisons with atmospheric opacity measurements, temporal changes in Pancam albedo values provide insights into interactions between the Martian surface and atmosphere. Pancam observations are also used to “ground truth” measurements from orbit and validate radiometric calibrations, and we present comparisons across the full rover traverses to MOC, CTX, and MRO High Resolution Imaging Science Experiment (HiRISE) data. Albedo averages from the same regions observed by Pancam and all three orbital instruments generally agree to within ± 15%. The few instances found where cross-instrument comparisons exceed the estimated instrument calibration uncertainties can be attributed to atmospheric effects and/or differences in viewing geometries.

Improving Dynamic and Tribological Behaviours by Means of a Mn–Cu Damping Alloy with Grooved Surface Features

In this work, the effect of the damping component with/without individual grooved surface features on the friction-induced vibration and noise (FIVN) and surface wear performance is studied experimentally and numerically. The experimental results show that introducing a grooved damping component in the system has a significantly improved capability in suppressing the generation of FIVN. In addition, it is observed that the friction system with a grooved damping component suffers slighter wear. Numerical results show good agreement with the FIVN events observed in the experimental test. Through analysing the deformation behaviour of damping component and the contact behaviour of the friction system during friction process, it is speculated that the deformation behaviour of damping component plays a significant role in affecting the contact pressure and FIVN behaviour. In addition, linking the vibration performance and wear evolution, the connection between damping, and vibration and wear behaviour is discovered, which can further explain why the friction system with a grooved damping component shows improved capability in suppressing the FIVN of friction system.

Imaging Atomic Scale Dynamics on III\u2013V Nanowire Surfaces During Electrical Operation

As semiconductor electronics keep shrinking, functionality depends on individual atomic scale surface and interface features that may change as voltages are applied. In this work we demonstrate a novel device platform that allows scanning tunneling microscopy (STM) imaging with atomic scale resolution across a device simultaneously with full electrical operation. The platform presents a significant step forward as it allows STM to be performed everywhere on the device surface and high temperature processing in reactive gases of the complete device. We demonstrate the new method through proof of principle measurements on both InAs and GaAs nanowire devices with variable biases up to 4 V. On InAs nanowires we observe a surprising removal of atomic defects and smoothing of the surface morphology under applied bias, in contrast to the expected increase in defects and electromigration-related failure. As we use only standard fabrication and scanning instrumentation our concept is widely applicable and opens up the possibility of fundamental investigations of device surface reliability as well as new electronic functionality based on restructuring during operation.

The effects of seasonal variations in rainfall and production on the aquifer and surface features of Rotorua geothermal field

The Rotorua geothermal field is a shallow geothermal reservoir lying directly beneath Rotorua City in New Zealand. It is renowned for an abundance of natural geothermal manifestations including the geysers and hot springs at Whakarewarewa. Over-exploitation of the geothermal resource in the 1970s leading to the decline of many active surface features was recognised and subsequently addressed by a change of management policy. A wellbore closure programme was instigated in 1986 by the New Zealand government which resulted in the recovery of some of the geothermal features. The monitoring programme continues through to the present day and provides valuable data which is used for the calibration of the new numerical model of the Rotorua system presented here. This model focuses on seasonal factors that control water level fluctuations in the geothermal reservoir as well as the behaviour of individual surface features. The matches of model temperatures with field data from individual surface features are very promising and the model may assist with sustainable management of the geothermal resource.

A model of the free surface dynamics of shallow turbulent flows

ABSTRACTUnderstanding the dynamic free surface of geophysical flows has the potential to enable direct inference of the flow properties based on measurements of the free surface. An important step is to understand the inherent response of free surfaces in depth-limited flows. Here a model is presented to demonstrate that free surface oscillatory spatial correlation patterns result from individual surface features oscillating vertically as they advect over space and time. Comparison with laboratory observations shows that these oscillating surface features can be unambiguously explained by simple harmonic motion, whereby the oscillation frequency is controlled by the root-mean-square water surface fluctuation, and to a lesser extent the surface tension. This demonstrates that the observed “complex” wave pattern can be simply described as an ensemble of spatially and temporally distributed oscillons. Similarities between the oscillon frequency and estimated frequency of near-bed bursting events suggest that oscillon behaviour is linked with the creation of coherent flow structures.

Texture-based segmentation with Gabor filters, wavelet and pyramid decompositions for extracting individual surface features from areal surface topography maps

Areal topography segmentation plays a fundamental role in those surface metrology applications concerned with the characterisation of individual topography features. Typical scenarios include the dimensional inspection and verification of micro-structured surface features, and the identification and characterisation of localised defects and other random singularities. While morphological segmentation into hills or dales is the only partitioning operation currently endorsed by the ISO specification standards on surface texture metrology, many other approaches are possible, in particular adapted from the literature on digital image segmentation. In this work an original segmentation approach is introduced and discussed, where topography partitioning is driven by information collected through the application of texture characterisation transforms popular in digital image processing. Gabor filters, wavelets and pyramid decompositions are investigated and applied to a selected set of test cases. The behaviour, performance and limitations of the proposed approach are discussed from the viewpoint of the identification and extraction of individual surface topography features.

The sun‐as‐a‐star solar spectrum

AbstractThe Sun is the only star for which individual surface features can be observed directly. For other stars, the properties of starspots, stellar rotation, stellar flares, etc, are derived indirectly via variation of star‐integrated spectral line profiles or their luminosity measurements. Solar disk‐integrated and disk‐resolved observations allow for investigations of the contribution of individual solar disk features to sun‐as‐a‐star spectra. Here, we provide a brief overview of three sun‐as‐a‐star programs, currently in operation, and describe recent improvements in observations and data reduction for the Integrated Sunlight Spectrometer (ISS), one of three instruments comprising the Synoptic Optical Long‐term Investigations of the Sun (SOLIS) system. Next, we discuss studies employing sun‐as‐a‐star observations (including Ca II K line as proxy for total unsigned magnetic flux and 2800 MHz radio flux) as well as the effects of flares on solar disk‐integrated spectra. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Morphologic segmentation algorithms for extracting individual surface features from areal surface topography maps

Areal segmentation, i.e. the partitioning of areal surface topography data into regions, has recently attracted significant research interest in surface metrology. In particular morphologic segmentation, i.e. partitioning into Maxwellian hills and dales—currently the only segmentation approach endorsed by ISO specification standards—has shown potential for capturing the salient traits of a surface, so that its surface texture can be better encoded by parameters. However, recent developments in dimensional metrology applied to structured surfaces with features of dimensions on the order of micrometres (micro-electromechanical system, microfluidics, etc), and many other studies aimed at characterizing individual features in unstructured surfaces (scratches, bumps, holes, etc), are showing the importance of segmentation for extracting localized features from areal data. In this work, morphologic segmentation is applied to a selected set of case studies of industrial relevance, involving structured, semi-structured and unstructured surfaces, where the main goal is not the assessment of surface texture, but the extraction of individual surface features. The examples are designed to provide an overview of the main advantages and issues when applying morphologic segmentation in a comprehensive set of application scenarios.

CHARACTERISING VEGETATED SURFACES USING MODIS MULTIANGULAR SATELLITE DATA

Abstract. Bidirectional Reflectance Distribution Functions (BRDF) seek to represent variations in surface reflectance resulting from changes in a satellite's view and solar illumination angles. BRDF representations have been widely used to assist in the characterisation of vegetation. However BRDF effects are often noisy, difficult to interpret and are the spatial integral of all the individual surface features present in a pixel. This paper describes the results of an approach to understanding how BRDF effects can be used to characterise vegetation. The implementation of the Ross Thick Li Sparse BRDF model using MODIS is a stable, mature data product with a 10 year history and is a ready data source. Using this dataset, a geometric optical model is proposed that seeks to interpret the BRDF effects in terms of Normalised Difference Vegetation Index (NDVI) and a height-to-width ratio of the vegetation components. The height-to-width ratio derived from this model seeks to represent the dependence of NDVI to changes in view zenith angle as a single numeric value. The model proposed within this paper has been applied to MODIS pixels in central Australia for areas in excess of 18,000 km2. The study area is predominantly arid and sparsely vegetated which provides a level of temporal and spatial homogeneity. The selected study area also minimises the effects associated with mutual obscuration of vegetation which is not considered by the model. The results are represented as a map and compared to NDVI derived from MODIS and NDVI derived from Landsat mosaics developed for Australia's National Carbon Accounting System (NCAS). The model reveals additional information not obvious in reflectance data. For example, the height-to-width ratio is able to reveal vegetation features in arid areas that do not have an accompanying significant increase in NDVI derived from MODIS, i.e. the height-to-width ratio reveals vegetation which is otherwise only apparent in NDVI derived from the higher resolution Landsat NCAS dataset.

Starspots: signatures of stellar magnetic activity

AbstractStarspots, just as Sunspots, are among the most obvious tracers and signatures of stellar surface magnetic activity. Emphasized already several decades ago as the origin for the rotationally modulated brightness of cool late-type stars, it is just now that we start to trace individual surface features in great enough detail to understand their magnetic behavior and interaction. Starspots also became the most important “noise” for detecting extra-solar planets and could possibly be decisive when it comes to detect another Earth. Since this is not a review, and because indirect imaging techniques are covered in other papers in this volume, I focus in this paper on some specific detections of starspots and introduce four new facilities particularly suited for starspot research in the near future.

Surface albedo observations at Gusev Crater and Meridiani Planum, Mars

During the Mars Exploration Rover mission, the Pancam instrument has periodically acquired large‐scale panoramic images with its broadband (739 ± 338 nm) filter in order to estimate the Lambert bolometric albedo of the surface along each rover's traverse. In this work we present the full suite of such estimated albedo values measured to date by the Spirit and Opportunity rovers along their traverses in Gusev Crater and Meridiani Planum, respectively. We include estimated bolometric albedo values of individual surface features (e.g., outcrops, dusty plains, aeolian bed forms, wheel tracks, light‐toned soils, and crater walls) as well as overall surface averages of the 43 total panoramic albedo data sets acquired to date. We also present comparisons to estimated Lambert albedo values taken from the Mars Global Surveyor Mars Orbiter Camera (MOC) along the rovers' traverses, and to the large‐scale bolometric albedos of the sites from the Viking Orbiter Infrared Thermal Mapper (IRTM) and Mars Global Surveyor/Thermal Emission Spectrometer (TES). The ranges of Pancam‐derived albedos at Gusev Crater (0.14 to 0.25) and in Meridiani Planum (0.10 to 0.18) are in good agreement with IRTM, TES, and MOC orbital measurements. These data sets will be a useful tool and benchmark for future investigations of albedo variations with time, including measurements from orbital instruments like the Context Camera and High Resolution Imaging Science Experiment on Mars Reconnaissance Orbiter. Long‐term, accurate albedo measurements could also be important for future efforts in climate modeling as well as for studies of active surface processes.

Designing liquid crystal alignment surfaces

We have previously shown that tilted micron-scale posts can be used to generate uniform liquid crystal alignment. By considering the geometry and symmetry of individual surface features in more detail, we have been able to demonstrate finer control of alignment, eliminate the need for tilted structures, and show multidomain alignment.

Structures Formed in Spin-Cast Films of Polystyrene Blends with Poly(butyl methacrylate) Isomers

For polystyrene blends with poly(butyl methacrylate), replacing poly(n-butyl methacrylate) by poly(tert-butyl methacrylate) results in modified topography of spin-cast films (holes dominating at a surface are exchanged with islands, or vice versa, such individual surface features are increased), decreased PBMA surface excess, but similar overall domain structure. Two series (PS/PnBMA and PS/PtBMA) of films with constant thickness and PBMA fraction 0 < Φ < 1, cast from toluene onto silicon wafers, were examined with atomic force microscopy, X-ray photoelectron spectroscopy, profiling and mapping mode of dynamic secondary ion mass spectrometry. Topography was analyzed with the integral geometry approach. Film structure formation was postulated to involve surface segregation, phase separation, and instability of the transient PBMA layer [a linear relation between Φ2 and averaged size of holes (islands) was observed for PS/PnBMA (PS/PtBMA)]. Structural changes caused by isomer exchange are related to glass tr...

Low-Energy Electron Microscopy of Surface Phase Transitions

▪ Abstract The use of low-energy electron microscopy (LEEM) to study reversible surface phase transitions is reviewed. Representative experiments are described that highlight the key advantages of LEEM: the ability to image surfaces in situ, at elevated temperature, with good spatial and temporal resolution. With these capabilities, the evolution of individual surface features—domains, facets, islands, steps, etc.—can be measured. Real-time and real-space imaging make LEEM a powerful tool for characterizing the thermodynamics and kinetics that govern surface phase transformations.