A new interpretation for the degradation phenomenon of ZnO varistors

The electrical degradation phenomena of zinc oxide-based varistors were studied using a high-energy current pulse and a.c. polarization at different temperatures. Activation energy measurements during the degradation process showed that these phenomena are associated with diffusion and that the diffusion-controlling species are slower than Zn., For degradation promoted by current pulses of 8×20 μs, the Schottky potential barrier deformation was measured. A decrease in height and width of the potential barrier due to the reduction of surface states density,N _s, without a significant change in donor density,N _d, was observed. To explain these results, a modification of the unstable components model is proposed for the potential barrier in which the degradation is due to oxi-reduction reactions between atomic defects. These reactions promote the elimination of zinc vacancies and/or adsorbed oxygen on the grain boundaries.     

Multilayered corrosion scales on metals and alloys: Experimental study of the sulfidation of a FeCrAl alloy and interpretation as a far-from-equilibrium phenomenon

The experimental study of the H₂S sulfidation of a Fe-22Cr-5.5 Al alloy, which leads to a multilayered scale, points out the existence of a critical temperature and a long time evolution of the layered scale. A detailed analysis of the experimental data shows that this could be explained by a kinetic approach involving non-linear processes.     

Cyclodextrin inclusion complexes of miconazole and econazole--isolation, toxicity on human cells, and confirmation of a new interpretation of the drug supersaturation phenomenon

Parameters that influence the precipitation of the beta-cyclodextrin (beta-CD) inclusion complexes of the antimycotics miconazole and econazole were investigated. The mechanistic reason for the superior antimycotic activity of the miconazole inclusion complex was studied. The toxicity of the complex was estimated. The temperature, the buffer strength, and the effect of the addition of hydrotropic agents on the CD solubility diagrams for the antimycotics were estimated. The miconazole and the CD dissolution rate for the complex was measured. The hemolytic activity of the miconazole inclusion complex, the physical mixture, miconazole, and the nitrate salt were compared. The toxicity on TR146 oral cell layers was measured. Lowering the temperature meant that both complexes precipitated at lower CD concentrations. Addition of hydrotropic agents and variation of the buffer strength affected the solubility diagrams. The dissolution medium was supersaturated with miconazole. The supersaturation was not disclosed by the traditional method to analyze for drug supersaturation. The miconazole complex was more toxic to erythrocytes than the physical mixture. On the other hand, the toxic effects of the two products on the TR146 cell layers were similar. Lowering the temperature eased the isolation of genuine CD inclusion complexes of miconazole and econazole. The miconazole supersaturation is likely to be the reason for the superior antimycotic activity of the complex. The complex and the physical mixture had about the same toxicity on TR146 cell layers.     

Mapping the frugal innovation phenomenon

This study aims at mapping the frugal innovation phenomenon. The study reveals that scholars affiliated with Indian institutes and originated from India have played a key role in this research discipline. Country wise, the highest number of frugal innovation cases is from India. The articles on frugal innovation have published in a wide range of disciplines and journals. Scholars, practitioners, and policy-makers have understood frugal innovation concept in various ways. Studies are predominantly in sectors, such as healthcare, electric and electronics, transport, finance, ICT, and energy. On the contrary, despite high importance, agriculture and education sectors have received limited attention.     

Alternative implementations of the Two-Mu algorithm

I describe implementations of the Two-Mu image-restoration algorithm that model the center portion of the convolution of the point-spread function and the original image (this has been done heretofore), as well as those that model the full range of that convolution. The full convolution methods produce processed images of simple, simulated scenes that are comparable in quality with, and often involve computations that are considerably shorter than, those of the center convolution methods. The full convolution methods incur some loss of information near the edge of the scene. However, that loss may not be significant for large images, especially for those in which the important information is far from the edge of the scene.     

Ringing phenomenon of the fiber ring resonator

A resonator fiber-optic gyro (R-FOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A fiber ring resonator is the core sensing element in the R-FOG. When the frequency of the fiber ring resonator input laser is swept linearly with time, ringing of the output resonance curve is observed. The output field of the fiber ring resonator is derived from the superposition of the light transmitted through the directional coupler directly and the multiple light components circulated in the fiber ring resonator when the frequency of the laser is swept. The amplitude and phase of the output field are analyzed, and it is found that the difference in time for different light components in the fiber ring resonator to reach a point of destructive interference causes the ringing phenomenon. Finally the ringing phenomenon is observed in experiments, and the experimental results agree with the theoretical analysis well.     

Numerical modelling of the hydrodynamic ram phenomenon

Hydrodynamic ram (HRAM) is a phenomenon that occurs when a high-kinetic energy object penetrates a fluid-filled container. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure, increasing the risk of catastrophic failure and excessive structural damage. This is of particular concern in the design of wing fuel tanks for aircraft since it has been identified as one of the important factors in aircraft vulnerability. In the present paper, the commercial finite-element code LS-DYNA has been used to simulate an HRAM event created by a steel spherical projectile impacting a water-filled aluminium square tube. Two different formulations (ALE and SPH) are employed to reproduce the event. Experimental tests which indicate the pressure at different points of the fluid, displacement of the walls and cavity evolution for different impact velocities are compared with the numerical results in order to assess the validity and accuracy of both ALE and SPH techniques in reproducing such a complex phenomenon.     

Some observations on the bowl phenomenon

Previous studies suggest that performance of a series system may be enhanced if those station(s) having smallest mean operation time requirement(s) and/or smallest variability are placed in the middle of the line. There has been considerable confusion relative to whether this ‘bowl phenomenon’ has to do with the placement of means, variances, or some combination of the two. The results of the current study show that the phenomenon observed is not related to an imbalance in means. Rather, it is associated with an imbalance in absolute variability. Furthermore, it is suggested that the bowl effect vanishes altogether in cases where a minimal level of in-process buffer stock is provided.     

The Internet phenomenon

The Internet presents a vision of unlimited knowledge in information, text, sound, images and film transmitted at low cost directly to the point required. Most people have heard of the Internet but the information available seems so endless as to be overwhelming. The article describes the origins and unique nature of this phenomenon. It categorises the main components of the Internet in order to provide a foundation of understanding on which to build. Briefly discussed are E-mail, Usenet, the World Wide Web, and remote access to library catalogues and databases     

Alternative analytical forms of the Fuchs-Sondheimer function

Starting from the Cottey conduction model and its extension, it is shown that the Fuchs-Sondheimer functions can be approximated by the extended Cottey function at any reduced thickness, provided that the specular electronic reflection coefficient,p, takes values larger than 0.31. Whatever the values ofp and the film thickness be an analytical formulation (in the form of the Cottey function) is proposed for an accurate approximation of the Fuchs-Sondheimer function. Moreover, it is suggested that the scattering processes defined in the Fuchs-Sondheimer model have no interaction.     

Probability interpretation of the levels of strength

A theoretical-probability model of the levels of strength and life observed by Bartenev is described. It is shown that on the empirical distribution function curves the levels of strength and life appear in the form of vertical steps of anomalous height. Their reproducibility in different samples of sufficiently large size is demonstrated. The probability of appearance of the levels and the rule of distribution of their population are found. A probability model of the test in the form of continuous-discrete random value, the integral distribution function of which has breaks at certain points, is proposed for interpretation of the levels of strength and life.Translated from Problemy Prochnosti, No. 5, pp. 79–82, May, 1990.     

Bezold-brücke phenomenon of the extrafoveal retina

With the use of an asymmetric matching technique, the Bezold-Brück phenomenon of the extrafoveal retina was measured at different eccentricities during the cone-plateau period of the long-term dark-adaptation curve and after 30 min dark adaptation. The results indicate that both the rod and the cone mechanisms contribute to the luminance-dependent hue shift of the extrafoveal retina.     

On the phenomenon of grain-boundary hardening in iron

Microhardness measurements on a fully recrystallized Fe-0.02 at. % W alloy show the existence of a region extending some 40 μm on either side of the grain boundaries, where the hardness is up to 35% higher than that of the grain. The magnitude of the hardening is partly controlled by the effective resolution of the hardness test because of the steeply increasing hardness near the boundaries. In addition, for small grain sizes, overlapping hardening profiles from the boundaries may affect the grain-interior hardness. The position of the boundary, with respect to the metallographic surface, significantly affects the width of the hardening; this width is increased on that side of the boundary where its inclination with respect to the surface of the specimen is increased. The results show that the excess, hardening at the boundary is a real hardening effect comparable to other hardening effects and that we should expect a marked inhomogeneity of bulk mechanical properties even for a relatively pure alloy.     

Concerning the erroneous interpretation of Langmuir's formulas

In computing the effective surface of a shell wall the corner correction should be divided by six, and not by three.