Development and validation of a computer attitude measure for young students (CAMYS)

An important aspect in successfully implementing instructional technology in educational settings is user acceptance, which is greatly influenced by users’ attitudes towards computers. Today, computers have become an integral part of instruction at all levels of education and it is important for educators and policy makers to understand how various factors interact with the user’s characteristics to influence the teaching and learning process involving the use of computers. Over the years, many scales have been developed to measure computer attitudes of secondary students and adults. Few have been develop to be used for students in the primary schools. The aim of this study is to develop and validate a computer attitude measure for young students (CAMYS). The revised 12-item CAMYS was piloted with 256 students aged 10–12 with a mean of 11.9 years (SD = 0.31). Several statistical analyses were performed to assess the reliability and validity of the measure. The measure, together with suggestions for administration and scoring are included.     

A Unified Curvature Definition for Regular,Polygonal, and Digital Planar Curves

In this paper, we propose a new definition of curvature, called visual curvature. It is based on statistics of the extreme points of the height functions computed over all directions. By gradually ignoring relatively small heights, a multi-scale curvature is obtained. The theoretical properties and the experiments presented demonstrate that multi-scale visual curvature is stable, even in the presence of significant noise. To our best knowledge, the proposed definition of visual curvature is the first ever that applies to regular curves as defined in differential geometry as well as to turn angles of polygonal curves. Moreover, it yields stable curvature estimates of curves in digital images even under sever distortions. We also show a relation between multi-scale visual curvature and convexity of simple closed curves.     

Learning directed probabilistic logical models: ordering-search versus structure-search

We discuss how to learn non-recursive directed probabilistic logical models from relational data. This problem has been tackled before by upgrading the structure-search algorithm initially proposed for Bayesian networks. In this paper we show how to upgrade another algorithm for learning Bayesian networks, namely ordering-search. For Bayesian networks, ordering-search was found to work better than structure-search. It is non-obvious that these results carry over to the relational case, however, since there ordering-search needs to be implemented quite differently. Hence, we perform an experimental comparison of these upgraded algorithms on four relational domains. We conclude that also in the relational case ordering-search is competitive with structure-search in terms of quality of the learned models, while ordering-search is significantly faster.     

Robust modeling of RC structures with an “event-by-event” strategy

The sequentially linear analysis is a robust alternative to nonlinear finite element analysis of structures when bifurcation, snap-back or divergence problems arise. The load–displacement response is captured by a series of linear analyses as a sequence of ‘events’. Every ‘event’ is a scaled critical state corresponding to the reaching of some peak of some saw-tooth for some softening element. Now, the approach is extended with a rippled saw-tooth curve which applies to any stress–strain diagram, including compression nonlinearity and yielding of reinforcement. Several RC structural examples demonstrate that both sharp snap-backs as well as ductile failures can be handled correctly.     

Size and boundary effects on desiccation cracking in hardened cement paste

The density of cracks or size of fragments formed in hardened cement paste upon first drying is affected by specimen size as measured with a crack-impregnation technique in free shrinking specimens with a thickness of 4 cm. Fragment size on the drying surface increased with distance away from the specimen corner, resulting in smaller average surface crack densities in larger specimens. Size effect on three- dimensional crack density, that was measured from sections through the impregnated specimens, was weaker. The size effect is explained by higher residual thermal stresses in larger specimens due to the cement hydration process. For comparison a desiccation crack pattern in a 5-mm-thick cement paste layer on a marble substrate was studied. Residual thermal stresses in this specimen were probably low and a uniform crack-pattern with a Gaussian-like fragment size distribution formed.     

InP based semiconductor structures for radiation detection

We report the preparation of semi-insulating InP single crystals of p-type conductivity and intentionally undoped p-type epitaxial layers for radiation detection. We focus on (i) the growth of InP single crystals doped with copper by the Czochralski technique and their subsequent temperature annealing to convert them to a semi-insulating (SI) state of p-type conductivity, and (ii) the growth of thick (>10 μm) p-type InP layers by liquid phase epitaxy with an admixture of Pr and Dy. Grown layers and single crystals were examined by low-temperature photoluminescence spectroscopy, capacitance-voltage and temperature dependent Hall measurements. An efficient purification due to rare earth (RE) admixture has been observed and layers grown with the addition of Pr and Dy exhibit the change of electrical conductivity from n to p at certain RE concentration in the melt. Dominant acceptors responsible for conductivity conversion have been identified. Three types of detection structures exploiting the Schottky or Schottky like contacts on pure and SI p-type InP or exploiting the p–n junction were designed.     

Influence of technological conditions on electronic transitions in chemical vapor deposited poly(azomethine) thin films

Thin films of poly(1,4-phenylenemethilidynenitrilo-1,4-phenylenenitrilomethilidyne) (PPI) have been prepared by chemical vapor deposition in the horizontal geometry using gaseous argon as a transport agent. PPI thin films have been grown by polycondensation of para-phenylene diamine (PPDA) and terephtal aldehyde (TPA). Fourier Transform Infrared spectra confirm formation of PPI layers without end groups. The strongest absorption band with discernible vibronic progression has been found to be due to superposition of 2.64, 2.82 and 3.03 eV bands corresponding to interband transitions connecting electronic ground state and vibrational levels of electronic excited state. A feature seen at about 2.6 eV in the spectra of PPI films prepared at higher temperatures of PPDA and TPA sources are attributed to excitons connected with the π-π? gap. Shoulder at 3.31 eV is attributed to interband transitions between delocalized states, while a peak at 4.2 eV is attributed to excitons formed by localized holes and delocalized electrons and vice versa and interband transitions connecting delocalized and localized bands, with the binding energy of about 0.8 eV. Thin films prepared at low temperatures of monomers consist of randomly distributed PPI chains weakly bound together.