Matte Surface Research Articles

Scaling up laser polishing using a polygon scanner

AbstractSurface roughness has a significant influence on the performance and appearance of components. By combining a boost laser with ultrafast beam deflection using a polygon scanner, very high processing speeds can be achieved. A 65 % improvement in surface roughness has been achieved on stainless steel, with Sa < 0.1 μm, while the gloss has increased from 130 to 366 GU. As a result, the previously matt surface became reflective, improving the appearance of the material. A real area rate of 156 cm2/s was achieved, comparable with industrial process times.

Frit-Free solar reflective porcelain stoneware ceramic tiles using recycled granite Waste: An investigation on its engobe and glaze formulations

The design of tiles can accelerate the transition of urban environments towards sustainability when building materials are prepared with sustainable, indigenous, renewable or recycled resources and additionally, present solar reflective properties for mitigating the Urban Heat Island (UHI) phenomenon. Here, an innovative approach to develop frit-free ceramics having solar reflectance property using locally sourced recycled granite waste was explored. The investigation unfolds in three parts: (i), the formulations were tailored for the engobe or glaze by varying raw material proportions; (ii), the solar reflectance was improved using whitening agents; and (iii), the selected formulations were subjected to an industrial trial casting of porcelain stoneware tiles. The full replacement of nepheline and feldspar with recycled granite powder offered properties suitable for the engobe such as a matte surface with high roughness and low gloss, while the same was identified to be less suitable in the glaze. The glaze formulation without any industrial frits was achieved by altering the proportions of nepheline and feldspar in the matrix. The solar reflectance of the engobe was enhanced by adding 10% of fine-grained zircon. The industrial trial showed that the developed formulation retained its conventional characteristics and superior functional performance in stain and chemical resistance.

Effect of surface finish and resin cement on the bond strength to CAD-CAM ceramics for interim resin-bonded prostheses

Statement of problemResin-bonded prostheses, including interim resin-bonded prostheses, are effective in preserving tooth structure compared with other types of fixed dental prostheses for the replacement of missing teeth. However, loss of retention remains a notable concern with these types of prostheses. PurposeThe purpose of this in vitro study was to investigate the influence of glass-ceramic type, resin type, and surface finish on the shear bond strength (SBS) to the CAD-CAM ceramics used to fabricate interim resin-bonded prostheses. Material and methodsEighty 10×2-mm glass-ceramic disks were fabricated by using a diamond saw (IsoMet 1000), 40 from feldspathic porcelain blocks (Vita Mark II) and 40 from lithium disilicate blocks (IPS e.max CAD). Half of the specimens in each group were left with a dull or matte surface finish after cutting, while the other half were glazed with an add-on glaze (VitaAkzento Plus Glaze Spray and IPS e.max CAD Glaze Spray, respectively). The disks were mounted in acrylic resin, and each group was subdivided into 2, with 1 receiving a photopolymerized resin cement (RelyX Veneer) and the other receiving a flowable composite resin (Filtek Supreme Ultimate Flow) to form 2.38×2-mm cylinders. SBS was determined using a universal testing machine (Instron 4411) in accordance with the International Organization for Standardization (ISO) 29022:2013 standard, and failure modes were analyzed by using a stereomicroscope with ×40 magnification. The data were analyzed with a 3-way analysis of variance and Tukey post hoc analysis. The chi-squared test was used to analyze the failure mode (α=.05 for all tests). ResultsCeramic type, resin type, and surface finish significantly impacted SBS (P<.001, P=.003, P<.001, respectively). Lithium disilicate showed higher SBS than feldspathic porcelain, and flowable composite resin exhibited higher SBS than resin cement. Glazed surfaces displayed lower SBS compared with the dull or matte surfaces. The combinations among the 3 materials also impacted SBS (P=.03). In addition, the combinations between ceramic type and surface finish affected SBS (P<.001), regardless of resin cement type. No other combinations affected the SBS (P>.05). The mode of failure was different among the groups (P<.001). In comparison with all other groups, cohesive failures were most prevalent in feldspathic porcelain with a dull or matte surface finish, regardless of the resin type used. ConclusionsThe SBS to glass-ceramics was influenced by ceramic material, resin cement type, and surface finish. Flowable composite resin showed higher SBS than resin cement. A dull or matte surface finish exhibited greater bond strength than a glazed surface. Lithium disilicate had higher SBS than feldspathic porcelain.

Влияние предварительной плазменной обработки поверхности стали 09Г2С на формирование покрытия в результате горячего цинкования

In recent years, the range of silicon-containing steels subjected to hot galvanizing has been expanding. Alloying of steel with 0.5–1 % of silicon leads to the formation of a zinc coating of great thickness with a matte or multi-colored surface. This is associated with the changes in phase reactions between iron and zinc in the Fe–Zn–Si system. The development of ways to neutralize the negative influence of silicon on the formation of zinc coating is an urgent task. The purpose of the work is to study the influence of preliminary plasma cutting and plasma surface hardening of 09G2S (S355J2) steel on the thickness and structure of zinc coating formed on treated surfaces. It was found that after plasma cutting, the structure of the surface layer of steel is martensite, and after plasma surface hardening, it is martensite and ferrite. Analysis of the change in microhardness from the steel surface to the middle showed that the hardened layer depth is 400 μm. A zinc coating consisting of a δ-phase and a ζ-phase is formed on the surface of the steel without pretreatment. On the surface of the steel after plasma treatment, a zinc coating is formed characteristic of low-silicon steels and consisting of the δ-phase, ζ-phase, and η-phase. It was found that the thickness of the zinc coating on the surface after plasma cutting is two times less than on the untreated surface, and the reduction in the coating thickness occurs due to a decrease in the ζ-phase thickness. A hypothesis was suggested that the martensite formation on the steel surface leads to the disappearance of the ordered FeSi phase and changes the phase equilibrium in the Fe–Zn–Si system. Consequently, preliminary plasma treatment of the steel surface allows controlling the structure and thickness of the resulting zinc coating and is therefore recommended for introduction into the hot galvanizing process of silicon-containing steels.

Agromorphological Purification of Farmer’s Seeds and Diversity of Corchorus olitorius Linn.

Corchorus olitorius is commonly cultivated by household women for livelihood in Togo. No database has been found for gene bank tractability in Togo. This study aims to contribute to a better knowledge of diversity in C. olitorius from Togo, thereby developing a database information on this neglected crop. Twenty-seven accessions were collected in the 5 ecological regions in Togo, on which experiments were conducted. First experiment was an accession purification in order to access pure genotypes, second experiment was an Agro-morphological characterization to give an identity to each genotype. RCBD design was considered with 3 replications and repeated in two ecological zones in Togo. The results showed accessions A24, A25 and A26 to be of pure source, other accessions were a mixed of genotypes. Qualitative data identified polymorphic characters among the genotypes, leaf margin was serrate (92.31%) or dentate (7.69%), with a Lanceolate or Ovate leaf shape, and a glossy (53.85%) and matte leaf surface (46.15%). Leaf colour were green (53.85%), dark green (38.46%), and light green (7.69%)); branching habits were either predominantly primary (92.31%) or predominantly secondary (7.69%). Five main clusters were structured from quantitative characters. Cluster II comprises only genotype1, which genetic distance is significantly isolated from other genotypes, this could be a good candidate for genetic improvement with genotypes from other clusters. The abstract should be concise and informative.

Electrodeposition of Soft Magnetic Fe-W-P Alloy Coatings from an Acidic Electrolyte

Fe-W-P coatings were deposited from a newly developed electrolytic bath. The effect of plating parameters, such as electrolyte current density and pH has been studied. It was found that the pH has a very strong effect on the phosphorous content of the coatings. Metallic-like, non-powdery alloys of Fe-W-P deposits with no cracks (lowly stressed) can be obtained at a lower pH (&lt;3), exhibiting high phosphorus (up to 13 at.%) and low tungsten (6 at.%) contents. At a higher pH (&gt;3), the composition changes to low phosphorus and high tungsten content, showing a matte, greyish, and rough surface. The applied current density also influences the morphology and the amount of phosphorous content. The deposits showed an amorphous structure for all samples with soft ferromagnetic properties.

Prediction of motion artifacts caused by translation in handheld laser speckle contrast imaging.

In handheld laser speckle contrast imaging (LSCI), motion artifacts (MA) are inevitable. Suppression of MA leads to a valid and objective assessment of tissue perfusion in a wide range of medical applications including dermatology and burns. Our study shines light on the sources of these artifacts, which have not yet been explored. We propose a model based on optical Doppler effect to predict speckle contrast drop as an indication of MA. We aim to theoretically model MA when an LSCI system measuring on static scattering media is subject to translational displacements. We validate the model using both simulation and experiments. This is the crucial first step toward creating robustness against MA. Our model calculates optical Doppler shifts in order to predict intensity correlation function and contrast of the time-integrated intensity as functions of applied speed based on illumination and detection wavevectors. To validate the theoretical predictions, computer simulation of the dynamic speckles has been carried out. Then experiments are performed by both high-speed and low-framerate imaging. The employed samples for the experiments are a highly scattering matte surface and a Delrin plate of finite scattering level in which volume scattering occurs. An agreement has been found between theoretical prediction, simulation, and experimental results of both intensity correlation functions and speckle contrast. Coefficients in the proposed model have been linked to the physical parameters according to the experimental setups. The proposed model provides a quantitative description of the influence of the types of illumination and media in the creation of MA. The accurate prediction of MA caused by translation based on Doppler shifts makes our model suitable to study the influence of rotation. Also the model can be extended for the case of dynamic media, such as live tissue.

Leslie’s ‘can’ using Arduino

The heat irradiated by a surface depends on its temperature, colour, and roughness. In this manuscript, we built a 3D-printed rotary platform to monitor the radiation emitted by different surfaces and their temperatures. Instead of using a cube, we used a can with four regions (black, white, shiny, and matt surfaces). An Arduino board is responsible for controlling a step motor that rotates the can and collects simultaneous data from an infrared sensor module and a thermometer. With this apparatus, the students can observe the infrared radiation intensity as a function of the surface.

ИССЛЕДОВАНИЕ СТРУКТУРЫ СПЛАВОВ СИСТЕМ Al‒Si,Mn‒Fe‒CoМЕТОДАМИ СКАНИРУЮЩЕЙ ЭЛЕКТРОННОЙ МИКРОСКОПИИ

Scanning electron microscopy (SEM) is one of the widely used modern microscopic techniques designed to obtain visual information about the microstructure of solid-phase objects (alloys, metals, etc.). The paper presents the areas of application of a scanning electron microscope (semiconductors; biology and medicine; chemical, petrochemical, mining industries; research laboratories). Examples of analysis of various structures of materials (high-entropy alloy, silumin, fracture structure of A5M aluminum alloy) obtained using the scanning electron microscope method are given. It is shown that rounded pores (1.3±0.1 µm) are present in the microstructure of the high-entropy alloy of the Mn-Fe-Co-Cr-Ni system. The reason for the formation of pores may be the specifics of the wire-arc additive manufacturing technology. The structure of the silumin of the AL-10%SI system demonstrates a multiphase, morphologically diverse character. Irradiation with an electron beam of silumin is accompanied by melting of aluminum along the interfaces with inclusions of the second phase. The fracture of an A5M aluminum sample destroyed under fatigue conditions has an ash-gray color and a highly rough matte surface. As a result of studying the deformation characteristics of commercially pure A5M aluminum, it was found that samples of commercially pure aluminum in the initial state reach critical deformation and fail on average at 18742±654 cycles. The use of a magnetic field of 0.1&nbsp;T of constant geometry leads to an increase in the number of cycles to failure by 36.8%, on ave-rage, the samples are destroyed at 25207±2349 cycles.

INCREASING THE EFFICIENCY OF FINISHING JET AND ABRASIVE PROCESSING OF SMALL PARTS

The article develops generalizing empirical mathematical models of the parameters of abrasivemachining of parts by submerged jets, which allow, according to the criteria of the least surfaceroughness and the highest productivity, to determine rational processing parameters. It has beenestablished that during processing, the edges of the parts are rounded, burrs, traces of corrosion andvarious inhomogeneities on the treated surfaces are eliminated, a uniform matte surface is formed with aroughness in the range of Ra = 0.8 - 1.25 μm, with hardening hardening (compressive stresses of depth 5– 6 μm), the complexity of processing is significantly reduced.

Development of Smart Bilayer Alginate/Agar Film Containing Anthocyanin and Catechin-Lysozyme.

Smart packaging can provide real-time information about changes in food quality and impart a protective effect to the food product by using active agents. This study aimed to develop a smart bilayer film (alginate/agar) with a cellulose nanosphere (CNs) from corncob. The bilayer films were prepared using 1.5% (w/w) sodium alginate with 0.25% (w/v) butterfly pea extract incorporated (indicator layer) and 2% (w/w) agar containing 0.5% (w/v) catechin-lysozyme (ratio 1:1) (active layer). The CNs were incorporated into the alginate layer at different concentrations (0, 5, 10, 20, and 30% w/w-based film) in order to improve the film's properties. The thickness of smart bilayer film dramatically increased with the increase of CNs concentration. The inclusion of CNs reduced the transparency and elongation at break of the smart bilayer film while increasing its tensile strength (p &lt; 0.05). The integration of CNs did not significantly affect the solubility and water vapor permeability of the smart bilayer film (p &gt; 0.05). The smart bilayer film displayed a blue film with a glossy (without CNs) or matte surface (with CNs). The developed bilayer film shows excellent pH sensitivity, changing color at a wide range of pHs, and has a good response to ammonia and acetic acid gases. The film possesses exceptional antimicrobial and antioxidant activities. The integration of CNs did not influence the antibacterial activity of the film, despite the presence of a higher level of DPPH in film containing CNs. The smart bilayer film was effectively used to monitor shrimp freshness. These findings imply that smart bilayer films with and without CNs facilitate food safety and increase food shelf life by monitoring food quality.

MODERN TRENDS IN THE DEVELOPMENT OF TECHNOLOGIES FOR MATTING GLASS PRODUCTS

Modern trends in the development of technologies for matting glass and glass products are considered. An effective technology of glass matting using alternative energy sources, in particular low-temperature plasma, has been developed. It is shown that when matting with iron powders with a dispersion of 160 and 450 microns, a high-quality matte surface of the “frosty” matting type is formed. The microstructure of the matted surface is investigated. Theoretical aspects of glass matting are considered. The technological parameters of matting are determined and the economic efficiency of the developed technology is shown.

On the Relationship between Contact Resistance and Load Force for Electrode Materials with Rough Surfaces.

Higher contact resistance not only increases power consumption and temperature rise but also causes undesirable interconnectivity between electrode materials, which further influences the electrical lifespan and reliability of switching devices. However, relevant studies on the relationship between contact resistance and load force, and on the reduction of contact resistance by controlling the micro-structure of rough surfaces, especially for electrode materials with larger Sq (root mean square) values, are very limited. In this study, the contact resistance calculation method, based on classical Holm theory in combination with the elastic and plastic deformation, was reviewed. Then, typical curves of measured contact resistance and load force were analyzed and compared with the calculation results for smooth surfaces. Furthermore, experimental results for electrodes with bright and matt surfaces were compared. It was found that the average contact resistance of samples with matt surfaces was 0.162 mΩ for a load force of 5 N, which decreased by 18.52% compared to that of the bright surface. The standard deviation of the contact resistance greatly decreased to 0.008 mΩ for samples with matt surfaces, which indicated that the matt electrode surface could effectively produce low and stable contact resistance. In addition, the influences of the numbers and sizes of contact a-spots on the relationship between contact resistance and load force were investigated. It was found that denser asperities with smaller curvature radii for the matt surface were beneficial for lower contact resistance, even for the electrode material with larger Sq values. Finally, an empirical model of the contact resistance with error bands based on the experimental results was established and verified.

ДОСЛІДЖЕННЯ СТАБІЛЬНОСТІ ДЕКОРАТИВНИХ ВЛАСТИВОСТЕЙ КОЛЬОРОВИХ ШЛАКОЛУЖНИХ БЕТОНІВ І РОЗЧИНІВ

The demand for decorative cements and the requirements for their characteristics are constantly growing. Particularly high demands are made on properties such as color stability under various operating conditions and resistance to efflorescence. In this work, studies of the stability of the properties of colored slag-alkaline concretes and plaster mortars were carried out in order to effectively control their decorative effect. Research is aimed at developing methods for controlling the decorative properties of materials based on these cements, which would be guaranteed to exclude the possibility of efflorescence and discoloration, regardless of their operating conditions. A set of methods was used to determine the tendency of slag-alkaline decorative concretes and plaster mortars to efflorescence and color fastness when exposed to ultraviolet radiation and steaming. The possibility of obtaining fast-hardening decorative slag-alkali cements of the 42.5R class and materials based on them using TiO2, kaolin and CaCO3 in the optimal amount as bleaching additives has been demonstrated. Mineral pigments of different colors and waste from alumina production ‒ red mud ‒ were used for coloring. It is shown that all decorative fine-grained slag-alkali concretes, regardless of the type of bleaching additive and pigment, do not have efflorescence. It is proved that during hardening and operation in indoor and outdoor conditions of atmospheric influences in the autumn-winter-spring period for 6 months, slag-alkaline decorative plaster coatings also had a fairly high resistance to the formation of efflorescence, and the addition of sodium carboxymethyl cellulose in the amount of 0.5% completely eliminates the risk of efflorescence, regardless of the hardening conditions of the plaster coating and operating conditions. Unlike plasters based on clinker decorative cements, which have an uneven shiny glossy surface after curing (which is highly undesirable), slag-alkali plaster coatings have a smooth, uniform matte surface. According to the research results, the color fastness of decorative slag-alkali cements to ultraviolet radiation and steaming is also high, their color after testing has not changed.

High Subsidence Rate After Primary Total Hip Arthroplasty Using a Zweymüller-type Noncemented Implant With a Matte Surface

Introduction:The surface topography is one key factor that affects the initial fixation of prosthesis in total hip arthroplasty (THA). We aimed to evaluate the mid-term results of a Zweymüller-type noncemented femoral implant (Elance stem) that had a matte surface with a target average roughness of 1.0 to 2.5 μm. The prosthesis was subjected to alkali and heat treatments to enhance its bone-bonding property.Methods:In this retrospective study, 30 THAs (27 patients) done using an Elance stem from September 2012 to October 2014 were evaluated clinically and radiographically for a mean follow-up of 6.3 ± 1.7 years after the index THA.Results:Stem revision was indicated for six hips (20%). The survival rate with stem revision for any reason was 86.4% (95% confidence interval, 68.9%-94.8%) at 5 years. Stem subsidence >5 mm was noted in 17 hips (56.7%). The survival rate with stem subsidence >5 mm as the end point was 46.6% (95% confidence interval, 29.9%-64.2%) at 5 years.Conclusion:The Zweymüller-type noncemented stem with a low-roughness matte surface demonstrated a high subsidence rate, although the bone-bonding property was potentially enhanced by the alkali and heat treatments. Surgeons should be aware that an insufficient surface roughness could lead to poor mechanical fixation of the noncemented stem, even with an appropriate stem geometry and surface chemistry.

Comb-like poly(dodecyl methacrylate) modified SiO2 nanoparticles as nanohybrid coatings: Electron beam grafting and tuning superhydrophobic/water-repellent surface studies

The current research focuses on tailoring silica nanoparticles (SiO2NPs) with comb-like poly(dodecyl methacrylate) (PDMA) brushes and tuning coating parameters based on roller coating process for confining surface morphology towards hydrophobic and superhydrophobic including water-repellent surface. Electron beam (EB) induced a simultaneous “graft-from” polymerization of DMA monomer onto vinyl modified SiO2NPs (SiO2NPs-V) was established in an inventive castor oil/ethanol mixed solvent. Functional surface chemistry of SiO2NPs and nanorough surface topography controlled by NPs content and coating thickness mainly influences the hydrophobic/superhydrophobic, water-repellent, and water absorption properties including gloss values, whiteness and yellowness index of coated papers. The papers coated with SiO2NPs-V-PDMA/PVA of 6–10 wt% with the thickness of ~10–14 μm exhibited matt surface and provided superhydrophobic and water-repellent properties. The coated paper has a desirable and stable water contact angle of 152°, low droplet adhesion with lower dynamic tilting angle (<5°), and 5.3-folds reduced water absorption. Our investigation provides compelling evidence that the SiO2NPs-V-PDMA obtained from EB modification and the developed coating formula for roller-based coating process are realistic approaches for hydrophobic/superhydrophobic coatings and printing inks for paper-based industries.

Smooth surface induced glossy appearance of freestanding multiwall carbon nanotube sheet

Carbon nanotube (CNT) structures reported in the literature often have a black color with low reflectance and matt surface appearance. Only a few papers reported the high reflectance and glossy appearance of the CNT surface on a substrate. To our knowledge, no one has reported the glossy appearance of freestanding CNT. Herein, we have successfully fabricated a freestanding multi-walled CNT sheet with a glossy or mirror-like surface appearance. Raman spectroscopy confirmed that both matt and glossy freestanding CNT sheets have the same chemical composition. We found that the glossy freestanding CNT sheet has a relatively flat surface morphology compared to matt freestanding CNT sheet, as seen in the atomic force microscopy results. We attributed the glossy appearance due to a relatively flat surface morphology of the freestanding CNT sheet.

Digital holography in production: an overview

Many challenging measurement tasks in production simultaneously have high requirements for accuracy, measurement field size, lateral sampling, and measurement time. In this paper, we provide an overview of the current state of the art in digital holography for surface topography measurements and present three applications from completely different productions with no alternative to digital holography; we describe the HoloTop sensor family, which has been designed specifically for industrial use, and present the most recent results achieved in real-life industrial applications. All applications address measurement tasks that could not be solved until now, either by optical or tactile means. We start with a description of the first-ever inline integration of a digital holographic measurement system that inspects precision turned parts for the automotive industry. We proceed by presenting measurements performed with a compact sensor that can be placed inside a tooling machine and operated fully wirelessly. In this case, the tool holder was used to position the sensor directly. Integration into a tooling machine places high demands on both robustness and reliability. Finally, the quality control of electronic interconnectors such as microbumps with the highest demand for accuracy and repeatability is demonstrated. All of these applications illustrate the major advantages of digital holographic systems: it is possible to measure a relatively large field of view with interferometric precision and very short acquisition times. Additionally, both reflective and matt surfaces can be measured simultaneously. We end this publication with an assessment of the future potential of this technology and the necessary development steps involved.

Effects of aging on the electrical properties of Au/n-Si/Ti, Cu/n-Si/Ti and AuCu/n-Si/Ti Schottky diodes

In this study, it is aimed to produce Au/n-Si/Ti, Cu/n-Si/Ti and AuCu/n-Si/Ti Schottky diodes and to calculate the diode parameters such as ideality factor, barrier height and series resistance by using time-dependent current–voltage (I-V) measurements. First, pure Ti metal was evaporated on the matt surface of the n-Si semiconductors and annealed at 420 ͦ C in nitrogen atmosphere. Secondly, Au and Cu metals and AuCu alloy were evaporated on the other surface of n-Si semiconductors. So, Au/n-Si/Ti, Cu/n-Si/Ti and AuCu/n-Si/Ti Schottky diodes were obtained. Finally, I-V measurements of the Schottky diodes were taken at specified time intervals (immediately,1, 7, 15, 30, 90, 180 and 365 days) and time-dependent diode parameters were calculated using the Thermionic Emission, Cheung and Norde methods.

Effect of curvature on hyperspectral reflectance images of cereal seed-sized objects

Hyperspectral imaging for quality and safety inspection of agricultural products is frequently confronted with the challenge of handling rounded surfaces. This challenge is especially noted when the objects are as small as cereal grains for which curvature with respect to the spatial dimension of a pixel is large. Diffusely reflected light from regions near the edges of a uniformly illuminated object the size of a wheat kernel will have its intensity reduced greatly, historically modelled by the Lambert Cosine Law, eponymously named after Johann Lambert of the sixteenth century, who theorised that the fraction of energy reflected from a spot on a matte surface is related to the declination angle of the observer. The current study was performed to compare the predicted Lambertian response of reflected light to actual measurement on curved surfaces of mathematically definable shapes, namely cylinders and prolate ellipsoids, with the latter introduced as an approximation to a wheat kernel. Carbon black-doped and sintered PTFE (0.16–0.99 nominal reflectance) cylinders of three diameters, with the smallest on par with the minor dimension of a wheat kernel, were scanned using a benchtop hyperspectral imaging system, as were dull gray-painted prolate spheroids of equivalent size and white wheat kernels. The analysis consisted of comparing the measured reflectances (940–1650 nm) from individual pixels along the curved surface with those determined according to the Lambert Cosine Law. The findings indicate that central pixels responded well to correction, with a greater departure from theory for pixels closest to the edges. • Hyperspectral images can be improved by treating objects as more than flat surfaces. • With Lambertian behaviour assumed, wheat is corrected by prolate spheroids. • Reflectance correction is best in central regions and worst near the trailing edges.