Studies of Detonation Characteristics of Aluminum Enriched RDX Compositions

Research on the effect of aluminum contents and of its particle size on detonation characteristics of RDX‐based compositions containing 15–60% aluminum was carried out. Measurements of detonation velocity for different charge diameters and confinements were performed. To measure the shock curvature of the detonation wave, X‐ray photography was applied. Unconfined charges and charges confined with a water envelope were tested. The radius of the detonation front curvature was determined. The cylinder test results were the basis for determination of the acceleration ability and energetic characteristics of the detonation products of the mixtures. The Gurney energy describing the acceleration ability was found. The detonation energy of the mixtures tested was also estimated from the cylinder test data.     

Quality assessment of ZnO-based varistors by 1/f noise

Noise has been used as a diagnostic tool of surge arrester varistor structures comprising of ZnO grains of various type and size. The physical and electrical properties of the measured samples have been described. In the experimental study, the applied measurement system and the results of noise measurements for the selected structures of varistors designed for the continuous working voltage 280 V, 440 V and 660 V have been presented. Noise properties are related to electrical characteristics of the measured specimens giving more distinctive results than their voltage–current characteristics. It is suggested that the proposed procedure can be applied as an effective non-destructive testing method focused on defects and structural heterogeneity detection in the tested objects to assess their preparation processes.     

Optimal design of a Kirchhoff-Love plate of variable thickness by application of the minimum principle

Structural and Multidisciplinary Optimization - An approximate thickness optimization of a rectangular Kirchhoff-Love plate with variable stiffness under uniform load is performed in this paper....     

On some convergence results for FDM with irregular mesh

The proof of convergence of the finite difference method with arbitrary irregular meshes for some class of elliptic problems is presented. By the use of the truncation error technique and stability analysis it was showed that $\text{max}{}_{\mathrm{i}}\text{¦u}{}^{\mathrm{i}}\text{? u}{}_{\mathrm{h}}{}^{\mathrm{i}}\text{¦? Ch}$, i.e., the solution u_h converges linearly with the size of the star. Correctness of this theorem was also confirmed by numerical tests.     

Thermodynamic study and the phase diagram of the Mg-Sn system

By means of concentration cells of the following type, Mg (l)MgCl2 in (LiCl-KCl)_eut (l)Mg-Sn (1), the partial thermodynamic data of Mg in Mg-Sn liquid solutions have been obtained in the composition range of 0.1 ≤X _Mg ≤ 0.75 and at temperatures from 950 to 1100 K. These values are compared with thermodynamic data reported in the literature and used for the evaluation to obtain a complete set of thermodynamic functions for phase diagram calculations and for further interpretation by the associate model. This model, which accepts the existence of ‘Mg₂Sn as-sociates’ in the liquid alloys, enables calculations of viscosity by Kucharski’s method corre-lating properly with experimental data. Mutual correlations between thermodynamic properties, physical properties, structure, and the phase diagram of the Mg-Sn system were shown to in-dicate a maximum chemical short-range order close to the composition Mg2Sn.     

Diagnosis of tool wear based on cutting forces and acoustic emission measures as inputs to a neural network

Cutting forces and acoustic emission measures as a function of tool wear are presented for different cutting parameters and their applicability for tool condition monitoring is evaluated. The best of them, together with cutting parameters, were chosen as inputs to a feedforward, back propagation (FFBP) neural network; some training techniques were applied and their effectiveness is also evaluated. Conventional training of FFBP neural networks very soon leads to overtraining, hence to deterioration in the net response. Training of these nets depends very much on the initial weight values. A good way of finding satisfactory results is to introduce random distortions to the weight system, which efficiently push the net out of a local minimum of testing errors. An even more effective method may be to employ temporary shifts in the weights, alternately negative and positive. This has two advantages: (1) it brings the net to balance between training and testing errors and (2) it enables a great reduction in the number of hidden nodes.     

Well-defined core-shell structures based on silsesquioxane microgels: Grafting of polystyrene via ATRP and product characterization

Silsesquioxane microgel nanoparticles characterized by low diameters (below 30 nm) and reduced polydispersity can be produced in an acid-catalyzed sol-gel process in an aqueous microemulsion. Suitable surface modification of such structures leads to macroinitiators for atom-transfer radical polymerization (ATRP). This polymerization method was applied in order to graft polystyrene chains onto the surface of the microgels. Well-defined structures exhibiting a core-shell architecture were produced with the M_w of grafted polymers ranging from 8.5 to about 30 kg/mol. The products were extensively characterized with light scattering, X-ray scattering, thermal analysis (TGA/DSC) and microscopy (TEM/SEM) to obtain information on parameters characterizing polystyrene brush. Polymer-grafted nanoparticles will be used for the modification of homopolymer and block copolymer matrices.