Digital parallelism, perpendicularity, and rectangles

The slope of digital line segments is defined and an algorithm to evaluate it is presented. Parallelism and perpendicularity of two digital line segments are also defined. Finally, rectangular digital regions are defined and characterized, and an algorithm that determines whether or not a given digital region is a digital rectangle is presented.     

Electrical characteristics of r.f.-sputtered CdTe thin-films for photovoltaic applications

A method of preparing self-doped p- and n-type and In-doped n-type CdTe thin-films for photovoltaic applications has been developed using r.f. sputtering. Ohmic contacts to n-type films with contact resistivity less than 10^?2 Ω — cm² have been obtained. Schottky barrier diode test devices, formed by evaporation of various metals including Au on n-CdTe films, have been examined for electrical and photovoltaic evaluation of the sputtered films. Although S.B. diodes based on In doped films, prepared under Cd overpressure, show promising electrical and photovoltaic performance (V_oc ～ 315 mV, I_sc ～ 4.6mA/cm²), much improvement remains to be made by further control of dopant concentration and structural details of films.     

On the dynamics of localization and fragmentation—III. Effect of cladding with a polymer

In this series of papers, we investigate the mechanics and physics of necking and fragmentation in ductile materials. The behavior of ductile metals at strain rates of about 4,000–15,000 per second is considered. The expanding ring experiment is used as the vehicle for examining the material behavior in this range of strain rates. In Part I, the details of the experiment and the experimental observations on Al 6061-O were reported. Statistics of necking and fragmentation were evaluated and the process was modeled through the idea of the Mott release waves both from necking and fragmentation. Finally, it was shown that the strain in the ring never exceeded the necking strain in regions that strained uniformly. In Part II, we addressed the issues of strain hardening, ductility, geometry and size. Specifically, we examined different materials—Al 1100-H14, and Cu 101—and concluded that geometric constraint influences the strain at onset of localization significantly. The time taken for the localization to propagate across the cross-section and begin to unload its neighborhood was shown to control the amount of strain that can be experienced by the material; this also influences the statistics of localization and fragmentation. In the present paper, Part III, we examine the influence of compliant polymeric claddings on the localization and fragmentation response of metallic materials. Thin aluminum rings were coated with a layer of polyurea, with the thickness being an important parameter in the study. The onset of necking localization is shown not to be influenced by the coating; however, the propagation of unloading or release waves is shown to be significantly impeded by the cladding and therefore, further straining and fragmentation of the rings is affected. This result is of great importance in determining the impact resistance of elastomer-clad metallic structures. In future contributions as part of this sequel, we will explore the effect the development of localization and fragmentation in tubes and sheets where the geometric constraint can be varied over an even larger range.     

Tree model based eco-climatic vegetation classification and fuzzy mapping in diverse tropical deciduous ecosystems using multi-season NDVI

Many vegetation classification strategies in tropical ecosystems involving conventional image processing of original satellite imagery bands require considerable prior site knowledge, statistical assumptions, and are difficult, expensive and inconsistent. In this paper we show that the intra-annual variation and rates of change in NDVI for different parts of a large forest area in combination with rules derived from a tree model can be used for detailed vegetation mapping. We used three-date NDVI data for the Biligiri Rangaswamy Temple Wildlife Sanctuary in Karnataka, southern India comprising mean NDVI, coefficient of variation (CV) and two NDVI change vectors corresponding to intraseasonal NDVI differences. A rule-based classification using a tree model was developed at two levels. The overall kappa statistic is 0.61 at level 1 classification, indicating a strong correspondence with the raster version of the available vector reference map based on ground data, even though the two maps are not strictly comparable. Several limitations of the available reference map have been highlighted by the new technique, especially the absence of ecotones. At level two the tree model map has provided detailed classification of dry deciduous forests and new classes not available in the reference map. The method in combination with reference data also provides a framework for fuzzy classification. This technique offers a relatively simple cost-effective alternative to existing classification strategies, especially for areas with diverse evergreen and deciduous vegetation elements.