Correlation between matrix structural order and compressive stress exerted on silicon nanocrystals embedded in silicon-rich silicon oxide

Abstract

Silicon nanocrystals embedded in a silicon oxide matrix were deposited by radio frequency reactive magnetron sputtering. By means of Raman spectroscopy, we have found that a compressive stress is exerted on the silicon nanocrystal cores. The stress varies as a function of silicon concentration in the silicon-rich silicon oxide layers varies, which can be attributed to changes of nanocrystal environment. By conducting the Fourier transform infrared absorption experiments, we have correlated the stresses exerted on the nanocrystal core to the degree of matrix structural order.

PACS

78.67.Bf, 78.67.Pt, 73.63.Bd, 78.47.D, 74.25.Nd     

The impact of different volume fractions of crystalline structures on the electrochemical behaviour of Mg67Zn29Ca4 alloys for biomedical applications

ABSTRACT

In this work, the influence of various volume fractions of the crystalline phase in an amorphous matrix of Mg₆₇Zn₂₉Ca₄ alloys was investigated for its corrosion resistance for biodegradable applications. An amorphous Mg₆₇Zn₂₉Ca₄ alloy was successfully fabricated using melt casting into a copper mould. Then, to obtain different ratios of the crystalline phase in an amorphous matrix, the obtained amorphous rods with 3?mm diameters were annealed at 190, 230, 250, and 400°C. The volume fraction of the crystalline phase was measured by X-ray diffraction, and the microstructures of the obtained alloys were determined based on scanning electron microscopy images. Electrochemical testing was conducted in simulated body fluid at 37°C. This report shows that the ratio of the volume fractions of amorphous and crystalline phases in alloy microstructures strongly influences their corrosion behaviours. The alloy with a fully amorphous structure was the most resistive in the analysed media.     

Experimental Results on the Fixed Matrix Regenerator Effectiveness for a Glass Stove Furnace

This paper presents experimental results on the effectiveness of regenerators working integrally with an open hearth glass furnace. The presented data refer to two apparatus of identical size and geometry arranged in parallel but operating in a one-period-shifted mode. The effectiveness figures with corresponding uncertainties for each unit have been determined by making use of experimental data accounting for both heating and cooling periods. For the heating period the effectiveness is bound within the range 0.8795 ± 0.0683 to 0.9272 ± 0.0715. Considering those for the cooling period the effectiveness holds 0.9142 ± 0.0305 to 0.9499 ± 0.0329, shown to be accompanied by a bit lower uncertainty. Due to the difference in effectiveness, averaging was applied to calculate mean effectiveness value measured as weighted based on the uncertainties for both periods. As the result, the final averaged effectiveness of the investigated regenerators was found to be within the ranges of 0.9153 ± 0.0278 to 0.9367 ± 0.0296.     

Electroorganic reactions. Part 57.† DDQ mediated anodic oxidation of 2-methyl- and 2-benzylnaphthalenes

Electron-rich 2-methyl and 2-benzylnaphthalenes are efficiently converted into the corresponding carboxaldehyde or ketone by mediated electrolysis in the presence of about 25 mol % of DDQ. The reaction conditions are simple (constant current, undivided cell of 500 ml volume, graphite electrodes, aqueous acetic acid at 80 °C) and the construction of a reaction profile (products vs charge) shows the intermediate formation of side-chain acetoxy and hydroxy derivatives and the parallel formation of a byproduct involving side-chain substitution by DDQ.     

Phonetic Alignment and Similarity

The computation of the optimal phonetic alignment andthe phonetic similarity between wordsis an important step in many applications in computational phonology,including dialectometry.After discussing several related algorithms,I present a novel approach to the problem that employsa scoring scheme for computing phonetic similarity between phonetic segmentson the basis of multivalued articulatory phonetic features.The scheme incorporates the key concept of feature salience,which is necessary to properly balance the importance of various features.The new algorithm combines several techniquesdeveloped for sequence comparison:an extended set of edit operations,local and semiglobal modes of alignment,and the capability of retrieving a set of near-optimal alignments.On a set of 82 cognate pairs,it performs better than comparable algorithms reported in the literature.     

Probabilistic Algorithms for the Wake-Up Problem in Single-Hop Radio Networks

We consider the problem of waking up n processors in a completely broadcast system. We analyze this problem in both globally and locally synchronous models, with or without n being known to the processors and with or without labeling of the processors. The main question we answer is: how fast we can wake up all the processors with probability 1 - ε in each of these eight models? In [12] a logarithmic waking algorithm for the strongest set of assumptions is described, while for weaker models only linear and quadratic algorithms were obtained. We prove that in the weakest model (local synchronization, no knowledge of n or labeling) the best waking time is O(n/log n). We also show logarithmic or polylogarithmic probabilistic waking algorithms for all stronger models, which in some cases gives an exponential improvement over previous results.     

Evolution of the distribution of density, accumulated deformation, and topological features of powdered cylindrical workpieces under the deforming broaching conditions. Communication 2. Evolution of the internal topology of hollow cylindrical blanks in strengthening their internal surfaces and simultaneous densification by broaching

Special features of the structure of the pore space of powdered bodies produced by deforming broaching and “conventional” axial compression have been analyzed. From the experimental data the possibility of the isolation of a particular constituent of the pore volume, which is related to the region of interparticle contacts has been discussed. The topological nonuniformity of the pore space of powdered compacts has been considered.     

Spatial averages for linear elements for two-parameter random field

The paper deals with the modelling of the soil medium as a random field. The necessity of using local random averages in numerical and analytical stochastic calculations are the main interest. The paper concentrates on linear elements and on the calculation of the variances and covariances of local random variables averaged over these elements. Several equations are derived by analytical integration, both for isotropic and anisotropic random fields. These should be useful for calculation, analysis and a better understanding of the influence of the geometry of elements and the value of parameters of random fields on the covariances of local averages.