Structural entropy in detecting background patterns of AFM images

Structural entropy was developed for detecting the type of localization in charge distributions on a finite grid, especially in mesoscopic electronic systems. However, it is possible to detect and analyze superstructures, i.e., topologies consisting of more structures with different types of localization properties. In the definition of the structural entropy, the von Neumann entropy of the system is divided into two parts: first, the extension entropy, which is simply the logarithm of the occupation number; the second part is the structural entropy. On a structural entropy versus logarithm of the spatial filling factor map, the different types of localizations follow different, well-characterized curves. Spatial filling factor measures the percentage of the “filled” (i.e., high intensity) pixels of the image.An atomic force microscopy (AFM) image can be interpreted as some kind of charge distribution on a grid: after normalization, the darkness (or lightness) of the pixels fulfills all the necessary conditions. AFM image artifacts can be detected by plotting the structural entropy versus the logarithm of the spatial filling factor maps of the images. Not only the type of an added large-scale Gaussian, parabolic, exponential, or other function can be identified, but also by careful study of the curves belonging to the structures, the parameters can be detected, too.     

Sensitivity analysis of a directional potential drop sensor for creep monitoring

Recent research efforts indicated that directional potential drop (PD) measurements could be exploited for in-situ creep monitoring. The present work investigates the sensitivity of such measurements with a square-electrode configuration to geometrical and material variations caused by creep. This measurement technique is based on a modification of the conventional PD technique as it measures simultaneously two resistance values in orthogonal directions. Under uniaxial stress condition, the ratio of the lateral and axial resistances is roughly proportional to the applied strain. Experimental tests showed that small anisotropic changes in the resistance ratio caused by directional effects of creep can be distinguished from potentially far larger isotropic changes caused by non-directional reversible and irreversible thermal effects. The sensitivity of the square-electrode PD sensor to geometrical and material variations was analyzed separately and the analytical predictions were validated by experimental tests in both cases. The directional PD technique was found to exhibit high sensitivity that allows the detection of elastic and plastic strains as low as 0.05%. Additional experimental results from an accelerated 400-hour creep test are presented to demonstrate the feasibility of this technique to monitor creep degradation in 304 stainless steel at 600 °C.     

Within-school social comparison: How students perceive the standing of their class predicts academic self-concept.

Results from prior research indicate that a student’s academic self-concept is negatively influenced by the achievement of others in his or her school (a frame of reference effect) and that this negative frame of reference effect is not or only slightly reduced by the quality, standing, or prestige of the track or school attended (a “reflected glory” effect). Going beyond prior studies, the present research used both between-school and within-school approaches to investigate frame of reference and reflected glory effects in education, incorporating students’ own perceptions of the standing of their school and class. Multilevel analyses were performed with data from 3 large-scale assessments with 4,810, 1,502, and 4,247 students, respectively. Findings from all 3 studies showed that, given comparable individual achievement, placement in high-achieving learning groups was associated with comparatively low academic self-concepts. However, students’ academic self-concept was not merely a reflection of their relative position within the class but also substantively associated with their individual and shared perceptions of the class’s standing. Moreover, the negative effects of being placed in high-achieving learning groups were weaker for high-achieving students. Overall, the studies support both educational and social psychology theorizing on social comparison. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Honoring Dr. Bimal K. Bose [Tributes]

As a leading figure in the broad area of industrial electronics, Dr. Bimal K. Bose has made outstanding contributions in the fields of power electronics and motor drives. He is an innovator, educator, and mentor to many members of the industry all over the world. As part of this special issue, this column pays tribute to his lifetime achievements.     

Chaotic encryption of speech signals

This paper introduces a speech encryption approach, which is based on permutation of speech segments using chaotic Baker map and substitution using masks in both time and transform domains. Two parameters are extracted from the main key used in the generation of mask. Either the Discrete Cosine Transform (DCT) or the Discrete Sine Transform (DST) can be used in the proposed cryptosystem to remove the residual intelligibility resulting from permutation and masking in time domain. Substitution with Masks is used in this cryptosystem to fill the silent periods within speech conversation and destroy format and pitch information. Permutation with chaotic Baker map is used in to maximize the benefits of the permutation process in encryption by using large-size blocks to allow more audio segments to be permutated. The proposed cryptosystem has a low complexity, small delay, and high degree of security. Simulation results prove that the proposed cryptosystem is robust to the presence of noise.     

3D reconstruction based on hard tissue microtome cross-section pictures in dentistry

The aim of this study was to examine the accuracy of the computerized 3D surface analyzing and volume measuring method in dentistry. Two different types of test objects were used in the first part of the measurements. Each sample of the two groups was cross-sectioned using a hard tissue microtome. The sections were photographed on both sides and were projected on a graphical tablet and analyzed using a computer program. The measured and calculated parameters were compared. In the second part, 200 microm thick horizontal sections were prepared from 11 human incisor roots using the hard tissue microtome. This way, five sections were prepared from the apical 2 mm of each root. The effects of section thickness and number were modeled by decreasing the inclusion rate of the obtained number of sections from 10 to 2 and its influence on the calculated results was determined. This method was suitable for the approximation and analysis of 3D parameters. The results indicated that using 200-300 microm section thickness, the measured values were approximately 8-21% lower than the real parameters.     

Richard Bright in Hungary: a reevaluation

Richard Bright, the highly respected physician and nephrologist at Guy's Hospital, had a strong liking for travel. In 1815 he traveled in Hungary and made very important observations about the country. His 762-page book, entitled Travels from Vienna through Lower Hungary has detailed, sometimes appreciative, sometimes very critical remarks and comments on Hungarian history, art, archeology, religion, the situation of nationalities, education, social conditions, law, farming, and mining. The Hungarians cherished the memory of Bright's travel in their country as reflected in several papers and on two commemorative tablets recognizing him as a true and sincere friend of Hungary.     

Buckling analysis with the aska program system

The theoretical and practical considerations involved in extending the very large, general purpose finite element program system ASKA to include linear buckling mode analysis are presented. The main analysis features and their software implementation are discussed in the context of modular processors and data operands. A broader interpretation of buckling load factors and modes in relation to mode superposition is given, and typical applications are presented to illustrate both classical bifurcation buckling analyses and buckling mode superposition response.     

The mechanism of the adsorption of alkyl xanthate species on galena

Oxidation of galena produced thiosulphate and sulphate ions at the mineral surface but flotation activity, using isopropyl xanthate as collector, was found to depend on the concentration of thiosulphate ions at the surface. It is proposed that the thiosulphate ion reacts with di-isopropyl dixanthogen formed by oxidation of xanthate ion in solution. It was demonstrated that these species react in homogeneous solution to give xanthate and xanthogen-thiosulphate ions. The proposed surface reaction may account for the formation of a layer of adsorbed xanthate ions and for the surface redox potential being raised to a value where more xanthate ions can be chemisorbed and where dixanthogen is stable.