Scale Texture Research Articles

Analysis of behavioural rejection of micro-textured surfaces and implications for recruitment by the barnacle Balanus improvisus

Experiments performed in the field and in the laboratory show that the barnacle, Balanus improvisus, preferentially settles on smooth surfaces. Settlement and recruitment of B. improvisus was evaluated on micro-textured surfaces with scales of surface texture ranging from 1 to 100 µm in profile heights. Surface texture with profile heights within a topographic range of 30-45 µm reduced settlement and recruitment by 92% as compared to smooth surfaces. The reduction in recruitment on micro-textured surfaces is best explained by behavioural responses to surface topography. Behavioural experiments show that cyprids have a higher propensity for smooth surfaces than for micro-textured surfaces. Cyprids spend more time exploring smooth surfaces and more time swimming when exposed to micro-textured surfaces. Micro-textured surfaces are more often rejected by cyprids after exploration than smooth surfaces. It is suggested that some scales of surface texture could be exploited to improve future anti-fouling techniques in geographical areas where Balanus improvisus is a severe fouling problem.

The effect of speckle filtering on scale-dependent texture estimation of a forested scene

Spatial fluctuations in microwave backscatter may be an important piece of information in discriminating tree stands. However, the presence of speckle in synthetic aperture radar (SAR) image data is a barrier to the exploitation of image texture. The authors explored a new methodology that combines a recent adaptive speckle reduction algorithm by Lopes et al. (1990) with a generic texture estimation scheme. They investigated the claim that this filter was capable of preserving backscatter texture. To understand if speckle reduction was destroying backscatter texture, they compared the strength of the relationship between forest inventory parameters and image texture as a function of spatial scale for both filtered and unfiltered images. They used Radarsat Fine mode image data: single look resolution is approximately 8.5 m, and pixel spacing is 3 m. Their study area was northern Vancouver Island, B.C., on the west coast of Canada. For the unfiltered data, they found that the ability of image texture to predict the forest parameters decreased as the texture scale increased from 3 to 13 m, suggesting greater information content in the small scale texture. For the filtered data, this relationship was much weaker at small scales and was not a function of distance. Their results suggest that the speckle filter was not retaining small scale texture, which is consistent with the theoretical hypotheses underlying its multiplicative noise model. They also show that there is significant information in small state SAR image texture that may be used as an adjunct to other spatial information for discriminating tree stands in the temperate rain forest.

Macromorphology of polypropylene homopolymer tacticity mixtures

The macromorphology of isotactic/atactic (iPP/aPP) and isotactic/syndiotactic (iPP/sPP) polypropylene mixtures is examined by optical microscopy. The spherulitic macrostructure of equimolecular weight [weight-average molecular weight (Mw) = 200k] iPP/aPP blends is volume-filling to very high aPP concentrations when the crystallization temperature is 130 °C. Similar spherulitic macrostructures (spherulite size and volume-filling nature) are observed for iPP homopolymer and a 50/50 iPP/aPP blend at low crystallization temperatures (115–135 °C). At higher crystallization temperatures (140–145 °C), a equimolecular weight (Mw = 200k) 50/50 iPP/aPP blend exhibits nodular texture that blurs the spherulitic boundaries. Double temperature jump experiments show that the nodular texture is due to melt phase separation that develops prior to crystallization. The upper critical solution temperature (UCST) of a 50/50 iPP/aPP blend (Mw = 200k) lies below 155 °C, and the blend is miscible at conventional melt processing temperatures. The UCST behavior is controlled by the blend molecular weight and aPP microstructure. aPP microstructures containing increased isospecific sequencing (although still noncrystalline) exhibit a reduced tendency for phase separation in 50/50 mixtures (Mw = 200k) and the absence of nodular texture at low undercoolings (140–145 °C). Equimolecular weight (Mw = 200k) 50/50 iPP/sPP mixtures exhibit phase-separated texture at all crystallization temperatures. The size scale of the phase-separated texture decreases with decreasing crystallization temperature because of a competition between crystallization and phase separation from a melt initially well mixed from the initial solution blending process. Extended melt annealing experiments show that the 50/50 iPP/sPP mixture (Mw = 200k) is immiscible in the melt at conventional melt processing temperatures. The iPP/sPP pair shows a much stronger tendency for phase separation than the iPP/aPP polymer pair. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1947–1964, 2000

X-Ray Microbeam Diffraction Mapping of Different Texture Scales Important in Fatigue Cracking or in Large Deformations

AbstractPolychromatic synchrotron x-ray microbeam diffraction allows one to record Laue patterns simultaneously from all of the grains within the column of material irradiated. This paper describes 3-D texture mapping in polycrystalline Al and Cu samples. Transmission methods for determining the depths of diffracting volumes are outlined. The focus is on how the texture scale between micro- (i.e., individual grain orientations) and macro-texture defines fatigue crack paths in Al-Li 2090 T8E41: very large volumes of near single crystal material lead to large asperity formation, and at least forty volume percent of the material consists of these volumes. Results on grain subdivision in Cu after large deformations are also briefly reviewed.

A ‘non-local’ variational approach to the elastic energy minimalization of martensitic polycrystals

Solid-solid phase transformations in polycrystals are considered in the context of energy minimization. The energy of a single crystal is specified by a non-convex multi-well energy function, in the approximation of infinitesimal deformations. The number of wells corresponds to the number of distinct phases and each is assumed to have the same isotropic elastic modulus. The polycrystal's energy is defined a priori via minimization of the energy functional with proper account of the orientation distribution, with respect to all 'kinematically admissible' displacement fields.A variational principle of Hashin-Shtrikman type is derived for the polycrystal's energy by developing and generalizing the approach of Bruno and co-workers. The variational principle involves a non-local functional with a Green's function-related kernel operating on trial 'transformation fields' which are appropriately constrained to accommodate both the single crystal's constitutive law and the polycrystal's texture. For a statistically uniform polycrystal, the variational principle is reformulated to require minimization with respect to all possible two-point correlation functions of 'submicrostructure', compatible with the texture.This variational principle is applied to derive upper bounds for a statistically uniform polycrystal by employing a 'separation of scales', i.e. by constraining the set of trial fields to those with the property that the scale of the trial submicrostructure is much finer than the scale of the polycrystal's texture. Subsequent optimization with respect to this submicrostructure for each particular orientation reveals a connection with relaxation of a single crystal 'with fixed volume fractions' and associated H-measures as discussed by Kohn. The resulting upper bound is developed and compared with a bound derived by Bruno et al. For some examples the new bound is demonstrated to be sharper than the latter, as a result of an improved optimization procedure. The present approach also extends that of Bruno et al. to more general orientation distribution statistics and clarifies the effect of incompatibility of transformation strains in the single crystals for the overall performance of polycrystals.

Study of remote sensing image texture analysis and classification using wavelet

In the past one difficulty of texture analysis was the lack of adequate tools to characterize different scales of texture effectively. Recent developments in multiresolution analysis such as the Gabor and wavelet transforms, help to overcome this difficulty. This paper introduces a new approach to characterize texture at multiple scales. The performances of the wavelet transform are measured in terms of sensitivity and selectivity for the classification of 25 types of remote sensing texture relief images under the condition of different wavelet decomposition models, different filter lengths, different resolutions and different mother bodies. The reliability exhibited by texture signatures of wavelet transforms are beneficial for accomplishing segmentation, classification and subtle discrimination of texture.

Wavelet-based fractal signature analysis for automatic target recognition

Texture measures offer a means of detecting targets in back- ground clutter that has similar spectral characteristics. Our previous studies demonstrated that the ''fractal signature'' (a feature set based on the fractal surface area function) is very accurate and robust for gray- scale texture classification. This paper introduces a new multichannel texture model that characterizes patterns as 2-D functions in a Besov space. The wavelet-based fractal signature generates an n-dimensional surface, which is used for classification. Results of some experimental studies are presented demonstrating the usefulness of this texture mea- sure. © 1998 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(98)01001-0)

Growth mechanisms of metasomatic reaction veins in dolomite marbles from the Bergell Alps

Tremolite and olivine reaction veins in dolomite marble inclusions in the Bergell granite formed by a crack-reaction-seal mechanism during the cooling history of the area. Brittle failure of stressed marble opened extension cracks that served as conduits for infiltrating silica-rich aqueous fluids. Reaction of the fluids at 450–550 °C with dolomite along the fracture walls resulted in partial replacement of dolomite by reaction products whose mineralogy was controlled mostly by temperature. Aqueous silica dissolved in the fluid in the central fracture was transported by diffusion from the fracture wall to the reaction front in the dolomite marble. The velocity of the replacement reaction'front in the marble itself was controlled by the slower of the two processes: the surface-reaction kinetics of the replacement reaction and the diffusion rate of silica to the reaction site. Reaction veins with very different reaction front morphologies occur. Tremolite veins always have straight reaction fronts parallel to the central fissure and formed at about 450°C. Olivine veins are typically bounded by highly irregular, wavy, undulating reaction fronts. O1 veins formed at about 550 °C. It is concluded that Trmolite-vein growth was controlled by surface-reaction kinetics, whereas diffusion kinetics controlled the growth of olivine veins. The difference in the morphology of the reaction front surface is probably a consequence of small scale texture variations in the deposited vein rock and associated porosity differences. Both types of veins formed in about 1000 years.

Oxidation of niobium sheets at high temperature

This work shows the role of oxygen pressure on growth kinetics, morphology, phase composition and texture of oxide scale in the oxidation of niobium sheets at 900 °C. The particular morphology observed at low pressure shows the existence of competition between edge and surface growth mechanisms. Pressure and conversion rate influence the nature of preferential orientations of the Nb 2O 5 oxide layer: a [110] fibre axis is stabilized at high pressure but, at low pressure, the higher is the conversion rate, the more evident is this fibre axis. This behaviour is observed not only after cooling but also in situ. At high pressure, the evolution is not only temporal but also spatial: with increasing distance from the metal/oxide interface, a gradual transition from more oriented to randomly oriented layer is observed.

Spatiotemporal dynamics in the oxidation of groups IV–V metals: study of zirconium

This paper focus on the mechanism of zirconium oxidation at 850 °C by X-ray diffraction (XRD) and the interactions between chemical (oxide growth, phase proportion) and physical processes (oxide scale texture, mechanical stresses). The structural gradients in the oxide scale composed of monoclinic ZrO 2 (higher proportion) and tetragonal ZrO 2 were revealed by XRD at variable incidence. The spatial evolution of the monoclinic zirconia texture through the oxide scale was shown and quantified. Relaxation of the oxide compressive stresses was observed for different oxidation times and correlated to kinetic breakaway evidenced by other methods. A structural mechanism of the oxide formation is then proposed, which prove the interest of XRD in the investigations on heterogeneous kinetics.

Grain boundary studies of high-temperature superconducting materials using electron backscatter Kikuchi diffraction

Grain orientation and grain boundary misorientation distributions in high critical current density, high-temperature superconductors were determined using electron backscatter Kikuchi diffraction. It is found that depending on the type of superconductor and the processing method used to fabricate it, there exist different scales of biaxial texture from no biaxial texture, local biaxial texture, to complete biaxial texture. Experimentally obtained grain boundary misorientation distributions (GBMDs) were found to be skewed significantly to low angles in comparison to what is expected on the basis of macroscopic texture alone, suggesting that minimization of energy may be a driving force during the processing of high critical current density materials. In addition, a higher than expected fraction of coincident-site lattice boundaries is observed. Examination of maps of grain boundary misorientations in spatially correlated grains, i.e. the grain boundary mesotexture, suggests the presence of percolative paths of high critical current density. A combination of orientation measurements, theoretical modeling of GBMDs and modeling of percolative current flow through an assemblage of grain boundaries is performed to gain an insight into the important microstructural features dictating the transport properties of high-temperature superconductors. It is found that maximization of low energy, in particular, low-angle boundaries, is essential for higher critical currents. The combination of experimental and analytical techniques employed are applicable to other materials where physical properties are dominated by intergranular characteristics.

Modelling of melt segregation processes by high-temperature centrifuging of partially molten granites-I. Melt extraction by compaction and deformation

The present study deals with the experimental modelling of two different mechanisms of crystal-melt segregation in crustal rocks: (1) the buoyancy-driven compaction of the crystal + melt matrix and (2) melt filtering in a partially crystalline matrix due to differential stresses. These two segregation mechanisms have differing relative efficiencies in the deformation of crustal rocks and result in different texture scales depending on melt fraction, melt viscosity and tectonic stresses. A centrifuge furnace has been used in the present study for the modelling of melt migration in partially molten granitic rocks. Samples of Beauvoir granite (Massif Central, France) with a grain size of 0.16–0.5 mm and dimensions of diameter ∼5 mm, length ∼16 mm were used. These samples had been pre-fused at temperatures of 1000–1075 °C, yielding an initial average melt fraction of ∼45–50 volume per cent. The centrifuging of partially melted samples during ∼6 hr at an acceleration of 1000g (g is gravity) results in a linear vertical distribution of melt over the length of the sample without the development of a compaction layer. The gradient of the melt fraction (melt migrates to the top of samples) correlates with temperature: 1075°C ∼7 volume per cent mm-1; 1050°C ∼4 volume per cent mm-1; 1000°C ∼1.5 volume per cent mm-1. The calculated rate of melt migration varies from 3x10-5 cm s-1 (1075°C) to 2x10-6 cm s-1 (1000°C). Differential stresses of ∼0.7–1.4 MPa have been generated in the centrifuge by putting a piston (weight ∼1.02–2.05 g, diameter ∼4.5 mm) on the top of the partially melted sample, which is then centrifuged at ∼1000g. The rate of melt squeezing from the sample in this case is about two orders of magnitude higher than that observed without the piston. After centrifuging for 6 hr, a compaction layer below the piston is formed with a thickness of ∼2.5 mm and a crystal fraction of ∼70–65 volume per cent. Further centrifuging (∼15 hr) does not result in any increase of the compaction-layer thickness or volume percentage of crystals in it. The comparison of the two segregation mechanisms confirms the much greater efficiency of differential-stress-induced melt segregation and accumulation in veins and pockets than the compaction mechanism.

Effects of Ceria Coatings on Pure Iron Oxidation. Comparison with Extra Low Carbon Steels

A comparison of results obtained on blank and coated specimens shows that ceria coatings strongly modify the microstructure and texture of the wustite scale formed during low pressure oxidation of pure iron. On coated specimens, all the scale is composed of fast growing (200) oriented wustite grains ; crystallographic orientations (different from (200)) are no longer present in the wustite scale. The linear oxidation rates are always higher in the case of surface coated specimens due to the lack of epitaxial relationships with the metallic substrate. Cerium is located in the wustite matrix as a CeFeO 3 phase which dissolves in FeO in time. Carbon and manganese, present as major impurities in an Extra Low Carbon Steel, have a strong influence on oxidation kinetics and on the rare-earth element location in oxide scales. Carbon, diffusing slowly from the matrix bulk to the metal-scale interface, promotes spallation of the wustite scale, but carbon does not hinder CeFeO 3 formation. On the other hand, the manganese impurity prevents the formation of CeFeO 3 due to the lack of contact between the reducing FeO germs and the oxidant CeO 2 . This lack of contact is due to the high vapour pressure of manganese oxides, which evaporate at the beginning of the reaction, and promotes immediate CeO 2 coating spallation.

Wustite texture and microstructure modification by ceria surface addition during low pressure oxidation of pure iron at high temperatures

Pure iron oxidation is studied in the oxygen partial pressure ranging between p(O2 ) = 2.10-4 Pa and p(O2 ) = 4.10-2 Pa. These pressures were chosen in order to insure wustite formation in the temperature domain 700-950°C. Textural analysis with pole figure plotting is performed on specimens oxidized at 800 and 950°C in oxygen (partial pressure of p(O2 ) = 2.10-3 Pa). We have demonstrated that cerium coatings modify the microstructure and texture of a wustite scale grown on pure iron. All the resuits indicate that the main effect of the coating is to prevent the epitaxial relations between iron and the wustite scale. Then, the whole surface is covered by a fast growing scale. The pole figures show that the (200) planes of the wustite structure are mainly oriented parallel to the specimen surface. The [200] orientation is always associated to the faster growing scale. On blank specimens, the slow kinetic rate is attributed to the fact that the main part of the iron surface is covered by a wustite scale with orientation distinct from [200]. A good scale adherence was observed since the coating was sufficiently thin and regular to permit the (CeFeO3 ) cerium orthoferrite formation from the ceria coating. A perowskite type oxide appears as a good candidate for an homogeneous cerium introduction into oxide scales. Its formation is favoured by the iron external diffusion which looks like easy in the proceeding conditions.

Scaling violations with textures in two-dimensional phase ordering.

Scaling violations are found in the phase-ordering two-dimensional Heisenberg [O(3)] model, which has nonsingular topological textures, under dissipative nonconserved dynamics. Three separate length scales are found: ${\mathit{L}}_{\mathit{T}}$ characterizes the scale of individual textures, ${\mathit{L}}_{\mathit{N}}$ characterizes the separation between textures, and ${\mathit{L}}_{\mathit{C}}$ characterizes the distance between oppositely charged textures.

Nanometre scale textures in agate and Beltane opal

AbstractWe have carried out TEM observations of agates of geode origin and Beltane opals. Optically observable individual fibres in agates are composed of many fine fibres which consist of quartz crystallites of 8 to 100 nm in length stacked together parallel to <110> or <100> with c-axes perpendicular to the fibre elongation. The optically observable systematic striations in agate are found to consist of cyclic alternation of layers due to variation in grain size and porosity. Large quartz crystals, protruding into the spaces of geodes, represent the last stage of formation of these bands, and are merely a continuation of the banding sequence. Nanometre scale textures of cristobalite fibres were revealed in Beltane opals. The cristobalite crystallites have the size of 3 to 20 nm in length and are also stacked together. Our TEM results suggest that embryonic particles were formed in their corresponding growth environments and agglutinated to form fibres.

Ultrasonic studies of preserved peaches

Abstract A conventional clinical ultrasonic B-scanner has been successfully used to image preserved (canned) peaches, with a view to assessing the method's potential for detecting stone pits embedded in the peach flesh. In addition, it is suggested from the pictures obtained that the grey scale texture arising from the peach flesh may be indicative of variations in the degree of ripeness of the peach prior to preservation. The acoustic velocity and attenuation in the peaches appear to be close to those of soft tissues, and preliminary laboratory measurements confirm this.

1st- and 2nd-order motion and texture resolution in central and peripheral vision

Stimuli. The 1st-order stimuli are moving sine gratings. The 2nd-order stimuli are fields of static visual texture, whose contrasts are modulated by moving sine gratings. Neither the spatial slant (orientation) nor the direction of motion of these 2nd-order (microbalanced) stimuli can be detected by a Fourier analysis; they are invisible to Reichardt and motion-energy detectors. Method. For these dynamic stimuli, when presented both centrally and in an annular window extending from 8 to 10 deg in eccentricity, we measured the highest spatial frequency for which discrimination between ±45 deg texture slants and discrimination between opposite directions of motion were each possible. Results. For sufficiently low spatial frequencies, slant and direction can be discriminated in both central and peripheral vision, for both 1st- and for 2nd-order stimuli. For both 1st- and 2nd-order stimuli, at both retinal locations, slant discrimination is possible at higher spatial frequencies than direction discrimination. For both 1st- and 2nd-order stimuli, motion resolution decreases 2–3 times more rapidly with eccentricity than does texture resolution. Conclusions. (1) 1st- and 2nd-order motion scale similarly with eccentricity. (2) 1st- and 2nd-order texture scale similarly with eccentricity. (3) The central/peripheral resolution fall-off is 2–3 times greater for motion than for texture.

Discrimination of Norwegian farmed, ranched and wild‐origin Atlantic salmon, Salmo salar L., by image processing

Abstract A method of distinguishing between farmed, ranched and wild‐origin Atlantic salmon, Salmo salar L., using scale morphology is proposed. Circuli spacing and scale texture data, as expressed as a Fourier transform of transmission luminescent patterns. were extracted by image processing. Spacing patterns and texture features were most distinct for wild salmon compared with the other two groups. Three‐group quadratic discriminant function models were developed using different combinations of data types. The most efficient model to separate the three groups had a classification efficiency of 74%. When models were simplified to two groups, farmed and wild, efficiency increased to 90%, thus reflecting the feature overlap between farmed and ranched groups. The method may be a useful tool for more objective and efficient classification of wild versus husbandry‐origin salmon. However, it should be stressed that farmed salmon that escape at the smolt stage are still problematic.

Textural variations and impact history of the Millbillillie eucrite

Abstract— We have investigated 10 new specimens of the Millbillillie eucrite to study its textures and mineral compositions by electron probe microanalyser and scanning electron microscope. Although originally described as having fine‐grained texture, the new specimens show diversity of texture. The compositions (Mg/Fe ratios) of the host pigeonites and augite lamellae are homogeneous, respectively, in spite of the textural variation. In addition to their chemical homogeneity, pyroxenes in coarse and fine‐grained clasts are partly inverted to orthopyroxene. Chemical zoning of plagioclase during crystal growth is preserved. This eucrite includes areas of granulitic breccias and impact melts. Large scale textures show a subparallel layering suggesting incomplete mixing and deposition of impact melt and lithic fragments. An 39Ar‐40Ar age determination for a coarse‐grained clast indicates a strong degassing event at 3.55 ± 0.02 Ga. We conclude that Millbillillie is among the most equilibrated eucrites produced by thermal annealing after impact brecciation. According to the classification of impact breccias, Millbillillie can be classified as a mixture of granulitic breccias and impact melts. The last significant thermal event is characterized by network‐like glassy veins that run through clasts and matrices. Consideration of textural observations and requirements for Ar‐degassing suggests that the 39Ar‐40Ar age could in principle date either the earilier brecciation and annealing event or the event which produced the veins.