Optimal parameters of leader development in lightning

The dependences between the different parameters of a leader in lightning are obtained theoretically. The physical mechanism of the instability leading to the formation of the streamer zone is proposed. The instability has the wave nature and is caused by the self-influence effects of the space charge. Using a stability condition of the leader propagation, a dependence is obtained between the current across the leader head and its velocity of motion. The dependence of the streamer zone length on the gap length is also obtained. It is shown that the streamer zone length is saturated with the increasing of the gap length. A comparison between the obtained dependences and the experimental data is presented

Transition Property For Cube-Free Words

We study cube-free words over arbitrary non-unary finite alphabets and prove the following structural property: for every pair $(u,v)$ of $d$-ary cube-free words, if $u$ can be infinitely extended to the right and $v$ can be infinitely extended to the left respecting the cube-freeness property, then there exists a "transition" word $w$ over the same alphabet such that $uwv$ is cube free. The crucial case is the case of the binary alphabet, analyzed in the central part of the paper. The obtained "transition property", together with the developed technique, allowed us to solve cube-free versions of three old open problems by Restivo and Salemi. Besides, it has some further implications for combinatorics on words; e.g., it implies the existence of infinite cube-free words of very big subword (factor) complexity.Comment: 14 pages, 5 figure

Music Computer Technologies, Supply Chain Strategy and Transformation Processes in Socio-Cultural Paradigm of Performing Art: Using Digital Button Accordion

The article traces the transformation of the socio-cultural paradigm of button accordion performing as a dichotomy of traditional and innovative cultural directions. The authors carry out a diachronic analysis of the formation and development of electronic button accordion playing in the XX-XXI centuries, analyzing the psychoacoustic transformation of the socio-cultural perception of the musical electronic environment, identify the causes of social devolution of electronic button accordion in the XX century, and carry out a historical and cultural analysis of the process of the revival of performing on various modifications of electronic harmonicas in Russia. Performance on a digital button accordion is seen as a logical outcome of the evolution of the instrument accordion complex and the socialization of instrumentation in the new socio-economic conditions of the digital society. The article reveals the features of the formation of performance on a digital button accordion in the modern high-tech process of musical creativity, which opens up great prospects for contemporary forms of cultural and socio-cultural activity of a modern musician. Music and computer technologies are considered as an integral part of the cognitive-creative component of the work of the modern musician of the digital age

Theoretical and experimental study of high-pressure synthesized B20-type compounds Mn1−x_{1-x}(Co,Rh)x_xGe

The search and exploration of new materials not found in nature is one of modern trends in pure and applied chemistry. In the present work, we report on experimental and \textit{ab initio} density-functional study of the high-pressure-synthesized series of compounds Mn$_{1-x}$(Co,Rh)$_x$Ge. These high-pressure phases remain metastable at normal conditions, therewith they preserve their inherent noncentrosymmetric B20-type structure and chiral magnetism. Of particular interest in these two isovalent systems is the comparative analysis of the effect of $3d$ (Co) and $4d$ (Rh) substitution for Mn, since the $3d$ orbitals are characterized by higher localization and electron interaction than the $4d$ orbitals. The behavior of Mn$_{1-x}$(Co,Rh)$_x$Ge systems is traced as the concentration changes in the range $0 \leq x \leq 1$. We applied a sensitive experimental and theoretical technique which allowed to refine the shape of the temperature dependencies of magnetic susceptibility $\chi(T)$ and thereby provide a new and detailed magnetic phase diagram of Mn$_{1-x}$Co$_x$Ge. It is shown that both systems exhibit a helical magnetic ordering that very strongly depends on the composition $x$. However, the phase diagram of Mn$_{1-x}$Co$_x$Ge differs from that of Mn$_{1-x}$Rh$_x$Ge in that it is characterized by coexistence of two helices in particular regions of concentrations and temperatures.Comment: 12 pages, 11 figure

The quality of service paradigm as the focus of net-centric computing: a postgraduate course

In the past three years a new postgraduate elective course on Net-centric computing was developed for a Master’s degree in Information Technology. The course evolved around the core subject topics included in the Computer Science body of knowledge as suggested by the IEEE Computer Society/ACM Task Force in the Computing Curricula 2001 report, with a strong emphasis on the relationship between networking technology and the applications delivered in a global networked environment