The extended Malkus-Robbins dynamo as a perturbed Lorenz system

Recent investigations of some self-exciting Faraday-disk homopolar dynamo ([1-4]) have yielded the classic Lorenz equations as a special limit when one of the principal bifurcation parameters is zero. In this paper we focus upon one of those models [3] and illustrate what happens to some of the lowest order unstable periodic orbits as this parameter is increased from zero

A simple formula for the L-gap width of a face-centered-cubic photonic crystal

The width $\triangle_L$ of the first Bragg's scattering peak in the (111) direction of a face-centered-cubic lattice of air spheres can be well approximated by a simple formula which only involves the volume averaged $\epsilon$ and $\epsilon^2$ over the lattice unit cell, $\epsilon$ being the (position dependent) dielectric constant of the medium, and the effective dielectric constant $\epsilon_{eff}$ in the long-wavelength limit approximated by Maxwell-Garnett's formula. Apparently, our formula describes the asymptotic behaviour of the absolute gap width $\triangle_L$ for high dielectric contrast $\delta$ exactly. The standard deviation $\sigma$ steadily decreases well below 1% as $\delta$ increases. For example $\sigma< 0.1$ for the sphere filling fraction $f=0.2$ and $\delta\geq 20$. On the interval $\delta\in(1,100)$, our formula still approximates the absolute gap width $\triangle_L$ (the relative gap width $\triangle_L^r$) with a reasonable precision, namely with a standard deviation 3% (4.2%) for low filling fractions up to 6.5% (8%) for the close-packed case. Differences between the case of air spheres in a dielectric and dielectric spheres in air are briefly discussed.Comment: 13 pages, 4 figs., RevTex, two references added. For more info see http://www.amolf.nl/external/wwwlab/atoms/theory/index.htm

Photonic Band Gaps of Three-Dimensional Face-Centered Cubic Lattices

We show that the photonic analogue of the Korringa-Kohn-Rostocker method is a viable alternative to the plane-wave method to analyze the spectrum of electromagnetic waves in a three-dimensional periodic dielectric lattice. Firstly, in the case of an fcc lattice of homogeneous dielectric spheres, we reproduce the main features of the spectrum obtained by the plane wave method, namely that for a sufficiently high dielectric contrast a full gap opens in the spectrum between the eights and ninth bands if the dielectric constant $\epsilon_s$ of spheres is lower than the dielectric constant $\epsilon_b$ of the background medium. If $\epsilon_s> \epsilon_b$, no gap is found in the spectrum. The maximal value of the relative band-gap width approaches 14% in the close-packed case and decreases monotonically as the filling fraction decreases. The lowest dielectric contrast $\epsilon_b/\epsilon_s$ for which a full gap opens in the spectrum is determined to be 8.13. Eventually, in the case of an fcc lattice of coated spheres, we demonstrate that a suitable coating can enhance gap widths by as much as 50%.Comment: 19 pages, 6 figs., plain latex - a section on coated spheres, two figures, and a few references adde

Structure and phase composition of complex refractory coating and of the reaction zone of interaction with single-crystal alloy ZhS36-VI after high-temperature holds

A complex coating consisting of three layers, i.e., a gas-circulation coating and a two-layer ion-plasma coating with an internal Ni - Cr - Al - Ta - Re - Y layer and an external Al - Ni - Cr - Y layer for protecting single crystal turbine rotor blades from high-temperature oxidation is considered. The fine structure and the phase composition of the complex coating and of the reaction zone of interaction with single-crystal alloy ZhS36-VI after high-temperature holds in a range of 1050 - 1300 C for 1-1000 h are studied. © 2013 Springer Science+Business Media New York

Resonance-Induced Effects in Photonic Crystals

For the case of a simple face-centered-cubic photonic crystal of homogeneous dielectric spheres, we examine to what extent single-sphere Mie resonance frequencies are related to band gaps and whether the width of a gap can be enlarged due to nearby resonances. Contrary to some suggestions, no spectacular effects may be expected. When the dielectric constant of the spheres $\epsilon_s$ is greater than the dielectric constant $\epsilon_b$ of the background medium, then for any filling fraction $f$ there exists a critical $\epsilon_c$ above which the lowest lying Mie resonance frequency falls inside the lowest stop gap in the (111) crystal direction, close to its midgap frequency. If $\epsilon_s <\epsilon_b$, the correspondence between Mie resonances and both the (111) stop gap and a full gap does not follow such a regular pattern. If the Mie resonance frequency is close to a gap edge, one can observe a resonance-induced widening of a relative gap width by $\approx 5$.Comment: 14 pages, 3 figs., RevTex. For more info look at http://www.amolf.nl/external/wwwlab/atoms/theory/index.htm

УПРАВЛІННЯ ОБОРОТНИМИ АКТИВАМИ В КОНТЕКСТІ МАКРОЕКОНОМІЧНОГО РОЗВИТКУ

There is made an analysis of types of economic activity by their share in current assets in the economy of Ukraine in the article. There were determined the types of economic activity with the largest share of receivables (real estate transactions, agriculture, forestry, industry, financial and insurance activities), their contribution to GDP and their development tendencies were determined. There is presented a description of macroeconomic factors affecting the accounts payables and receivables of agricultural enterprises and industry. There are determined the types of economic activity with the largest volume of stocks in economy (industry, wholesale and retail trade, repair, agriculture). It is estimated the dynamics and the share of current financial investments and cash, it is proved the influence of the economic situation in the country on their formation and use. There were made some recommendations on efficient management of accounts receivable, inventories, current financial investments and cash.Проведен анализ видов экономической деятельности по их доли в оборотных активах в экономике. Установлены виды экономической деятельности с наибольшей долей дебиторской задолженности, оценена их вклад в ВВП и установлены тенденции развития. Определены макроэкономические факторы, влияющие на кредиторско-дебиторскую задолженность. Оценено динамику и долю запасов, текущих финансовых инвестиций, денежных средств, доказано влияние экономической ситуации в стране на их формирование и использование. Даны рекомендации по эффективному управлению элементами оборотных активов. Проведено аналіз видів економічної діяльності за їх часткою в оборотних активах в економіці. Встановлено види економічної діяльності з найбільшою часткою дебіторської заборгованості, оцінено їх вклад у ВВП та встановлено тенденції розвитку. Визначено макроекономічні чинники, що впливають на кредиторсько-дебіторську заборгованість. Оцінено динаміку та частку запасів, поточних фінансових інвестицій, грошових коштів, доведено вплив економічної ситуації в країні на їх формування і використання. Подано рекомендації щодо ефективного управління елементами оборотних активів

Photonic crystals of coated metallic spheres

It is shown that simple face-centered-cubic (fcc) structures of both metallic and coated metallic spheres are ideal candidates to achieve a tunable complete photonic bandgap (CPBG) for optical wavelengths using currently available experimental techniques. For coated microspheres with the coating width to plasma wavelength ratio $l_c/\lambda_p \leq 10$ and the coating and host refractive indices $n_c$ and $n_h$, respectively, between 1 and 1.47, one can always find a sphere radius $r_s$ such that the relative gap width $g_w$ (gap width to the midgap frequency ratio) is larger than 5% and, in some cases, $g_w$ can exceed 9%. Using different coatings and supporting liquids, the width and midgap frequency of a CPBG can be tuned considerably.Comment: 14 pages, plain latex, 3 ps figures, to appear in Europhys. Lett. For more info on this subject see http://www.amolf.nl/research/photonic_materials_theory/moroz/moroz.htm

Multiplicity Fluctuations in the Pion-Fireball Gas

The pion number fluctuations are considered in the system of pions and large mass fireballs decaying finally into pions. A formulation which gives an extension of the model of independent sources is suggested. The grand canonical and micro-canonical ensemble formulations of the pion-fireball gas are considered as particular examples.Comment: 13 pages, 4 figure

Rashba effect in 2D mesoscopic systems with transverse magnetic field

We present semiclassical and quantum mechanical results for the effects of a strong magnetic field in Quantum Wires in the presence of Rashba Spin Orbit coupling. Analytical and numerical results show how the perturbation acts in the presence of a transverse magnetic field in the ballistic regime and we assume a strong reduction of the backward scattering interaction which could have some consequences for the Tomonaga-Luttinger transport. We analyze the spin texture due to the action of Spin Orbit coupling and magnetic field often referring to the semiclassical solutions that magnify the singular spin polarization: results are obtained for free electrons in a twodimensional electron gas and for electrons in a Quantum Wire. We propose the systems as possible devices for the spin filtering at various regimes.Comment: 12 pages, 12 figures, to appear in Phys. Rev.

Законодавче регулювання обігу криптовалют в Україні, проблеми та перспективи їх розвитку

The rapid development of technological innovation is accompanied by changes in the transfer of settlements in electronic format, which leads to the emergence of new payment instruments. With the development of information technology there are many new and diverse forms of money, including electronic money and cryptocurrency. In connection with the rapid introduction of innovations in the sphere of payment and settlement systems, in particular, the circulation of cryptocurrency, a number of issues arise concerning regulatory regulation and it practical using in the national payment system of Ukraine. In the course of the study the foreign experience of regulating the circulation of cryptocurrency is considered, in particular, the main positions of financial institutions are outlined. The position of the National Bank of Ukraine regarding the circulation of cryptocurrency in Ukraine and the main proposed changes in the legislative and normative regulation of the cryptocurrency treatment provided for the draft laws are highlighted. The problems of taxation of mining related to the using of virtual cryptocurrency for illegal transactions, drug trafficking in arms and other prohibited goods, the loss of state monopoly on the issue of money, the reduction of the benchmark of central banks, the decrease in demand for national currency, which leads to its depreciation of the rate of turnover, which in turn complicates the process of determining the speed of money and the conduct of monetary regulation, the impossibility of an effective monetary policy, reducing the level of influence and elimination of financial intermediaries, etc.Legalization of cryptocurrency will help fill the revenue side of the state budget. And the issue of legal regu lation of cryptocurrency on the territory of Ukraine is relevant and necessary, as international experience shows, cryptocurrency is becoming increasingly popular in international practice, and it is virtually impossible and economically impractical to stop its development. The emergence of cryptocurrency with a high degree of financial novelty leads to revolutionary changes in monetary relations, and puts us at a new stage in the evolution of money. It causes new challenges on the monetary and payment systems and prompts governments to adapt their financial institutions accordingly. The main directions of improvement of the regulation of the cryptocurrency turnover are outlined on the basis of comparison of the current legislation in Ukraine with the economically developed countries of the European Union and the world.Швидкий розвиток технологічних інновацій супроводжується змінами в перенесенні розрахунків у електронний формат, що зумовлює появу нових платіжних інструментів. Із розвитком інформаційних технологій виникає багато нових і різноманітних форм грошей, зокрема електронні гроші та криптовалюти. Розглянуто зарубіжний досвід регулювання обігу криптовалют, зокрема окреслено основні позиції фінансових інституцій. Висвітлено позицію НБУ стосовно обігу криптовалют в Україні та запропоновано зміни законодавчо-нормативного регулювання обігу криптовалют, що передбачені у проектах законів. Проаналізовано проблеми оподаткування майнінгу, пов'язані з використанням віртуальних криптовалют для нелегальних трансакцій, торгівлі наркотиками, зброєю та іншими забороненими товарами, втрати державної монополії на емісію грошей, зниження сеньйоражу центральних банків, зменшення попиту на національну валюту, що зумовлює її знецінення, зміну швидкості обігу, що ускладнює процес визначення швидкості грошей і проведення грошово-кредитного регулювання, неможливість проведення ефективної грошово-кредитної політики, зменшення рівня впливу та усунення фінансових посередників та ін. Окреслено основні напрями вдосконалення регулювання обігу криптовалют на основі порівняння чинного в Україні законодавства з економічно розвиненими країнами Європейського Союзу та світу