Texture Units Research Articles

Vector choice in the texture spectrum approach

Abstract Recently the texture spectrum approach has been proposed as a statistical method for texture analysis, and applied to remotely sensed images. In the present study, this method is generalized to a space of M vectors and N grey level intervals for the elements of texture units, instead of M = 8 and N = 3 in the earlier studies of the texture spectrum. In this way, the texture unit set can be defined in a neighbourhood of 3 pixels by 3 pixels, 5 pixels by 5 pixels, 7 pixels by 7 pixels or other forms and sizes, and the co-occurrence matrix approach is unified to the texture spectrum method with the extreme case of M = 1. Several combinations of M and N have been evaluated to classify an imagery composed of six natural textures. The results show maximum discrimination for M = 5, followed by M = 4. In this way we minimize the calculation lime needed to maximize the accuracy of the classification.

Optical and crystallographic structure of pitch cokes

Carbonization of three different coal tar pitches (CTP) was carried out up to maximum temperature of 1200°, 1500°, 1800° and 2000°C, for five hours. The morphological and microtexture characteristics of the samples were examined by means of scanning electron microscopy and X-ray analysis. The development and rearrangement of the structure depending on high-temperature treatment (HTT) was followed by the type and size of the characteristic texture units present, as well as by crystallite height ( L c ) and interlayer spacing ( d 002). The influence of sulphur loss during HTT on pitch coke structural change was also examined. The parameters examined showed a marked interdependence.

Inflexibility in Selecting the Optical Basis for Perceiving Speed

Five subjects participated in an experiment designed to test if people could selectively attend to either edge rate (frequency of passing texture units) or flow rate (optical velocity of texture units) as the optical basis for controlling their own forward speed. Subjects continued to use edge rate as the basis for controlling forward speed, even when instructed to use flow rate and given feedback about their success in using it. The results are interpreted as evidence of inflexibility in selectively attending to information for self-speed.

Study of crystallization and isothermal thickening in polyethylene using SAXD, low frequency Raman spectroscopy and electron microscopy

This study contains a combined application of three different techniques for the study of polyethy-lenes crystallized from the melt under different circumstances, small-angle X-ray diffraction (SAXD), low frequency Raman spectroscopy to examine the longitudinal acoustic ( LA) mode, and electron microscopy. In particular, the combination of SAXD and Raman methods enables the separation of the situation where there is only one lamellar structure which displays several orders in the SAXD pattern, from that where there is more than one type of lamellar thickness present. The superior power of the Raman method, which does not depend on the regularity in the lamellar stacking, becomes apparent. The multiplicity of the lamellar population could be associated with lamellae formed isothermally at the preselected crystallization temperature and with lamellae which originated from material which has remained uncrystallized at this temperature and formed subsequently with smaller lamellar thickness during cooling of the sample. The existence of the corresponding double lamellar population could be made directly visible using electron microscopy on freeze-cut and stained sections. The thinner lamellae in the double population could be extracted by solvents, removing the corresponding SAXD and Raman peaks, and leaving blank image areas in place of the thin lamellae in the electron-micrographs. These extracted thinner lamellae correspond to lower molecular weights as assessed by g.p.c. Thus molecular segregation during crystallization is involved. Furthermore the segregated texture units and their arrangement within the full morphology could now be identified. Pronounced changes in lamellar thickness with crystallization time were observed throughout and were associated in the early stages of crystallization with molecular fractionation and in the later stages with thickening of lamellae already present. An unexpected interrelation between nucleation density and the final lamellar thickness through the agency of isothermal lamellar thickening has been established. Examples are quoted which are contrary to the expected trend of lamellar thickness with crystallization temperature, but which are interpretable nevertheless in the light of the effect of isothermal lamellar thickening. The potential significance of all these findings and of this kind of approach for the characterization of crystalline bulk polymers is made throughout.

The influence of texture density gradients on judgments of length

Adult Ss judged the relative lengths of pairs of surfaces viewed successively under restricted monocular conditions. Artificial deformations in the gradients of texture density derived from one surface in each pair had a significant influence on judged length. Surfaces on which the packing density of the texture units progressively increased toward the horizon were judged as longer than surfaces of equal physical dimensions but with evenly spaced texture elements.