Efficient spin control in high-quality-factor planar micro-cavities

A semiconductor microcavity embedding donor impurities and excited by a laser field is modelled. By including general decay and dephasing processes, and in particular cavity photon leakage, detailed simulations show that control over the spin dynamics is significally enhanced in high-quality-factor cavities, in which case picosecond laser pulses may produce spin-flip with high-fidelity final states.Comment: 6 pages, 4 figure

КРАУДФАНДИНГОВІ ТЕХНОЛОГІЇ У РОЗВИТКУ НАЦІОНАЛЬНОЇ ТУРИСТИЧНОЇ СИСТЕМИ

The article substantiates the sense of crowdfunding and determines a list of participants of crowdfunding projects. The author has proposed a scheme for implementation of a crowdfunding tourism project, indicating the main stakeholders. The author has substantiated directions of implementation of projects, using crowdfunding in the national tourism system. The author has suggested a “house” of crowdfunding for projects of the national tourism system. The article determines advantages and disadvantages of crowdfunding for the main stakeholders and the society.    В статье обоснована сущность краудфандинга и краудфандинговых технологий, определен круг их участников. Предложено процесс реализации краудфандинга туристического проекта с указанием основных стейкхолдеров. Обоснованы направления реализации проектов с помощью краудфандинга в туристической системе. Предложено «архитектонику» краудфандинга проектов национальной туристической системы. Определены преимущества и недостатки краудфандинга для основных стейкхолдеров и общества.У статті обґрунтовано сутність краудфандингу та краудфандингових технологій, визначено коло їх учасників. Запропоновано процес реалізації краудфандингу туристичного проекту із зазначенням основних стейкхолдерів. Обгрунтовані напрямами реалізації проектів за допомогою краудфандингу в туристичній системі. Запропоновано «архітектоніку» краудфандингу проектів національної туристичної системи. Визначено переваги та недоліки краудфандингу для основних стейкхолдерів та суспільства

Weak and strong coupling limits of the two-dimensional Fr\"ohlich polaron with spin-orbit Rashba interaction

The continuous progress in fabricating low-dimensional systems with large spin-orbit couplings has reached a point in which nowadays materials may display spin-orbit splitting energies ranging from a few to hundreds of meV. This situation calls for a better understanding of the interplay between the spin-orbit coupling and other interactions ubiquitously present in solids, in particular when the spin-orbit splitting is comparable in magnitude with characteristic energy scales such as the Fermi energy and the phonon frequency. In this article, the two-dimensional Fr\"ohlich electron-phonon problem is reformulated by introducing the coupling to a spin-orbit Rashba potential, allowing for a description of the spin-orbit effects on the electron-phonon interaction. The ground state of the resulting Fr\"ohlich-Rashba polaron is studied in the weak and strong coupling limits of the electron-phonon interaction for arbitrary values of the spin-orbit splitting. The weak coupling case is studied within the Rayleigh-Schr\"odinger perturbation theory, while the strong-coupling electron-phonon regime is investigated by means of variational polaron wave functions in the adiabatic limit. It is found that, for both weak and strong coupling polarons, the ground state energy is systematically lowered by the spin-orbit interaction, indicating that the polaronic character is strengthened by the Rashba coupling. It is also shown that, consistently with the lowering of the ground state, the polaron effective mass is enhanced compared to the zero spin-orbit limit. Finally, it is argued that the crossover between weakly and strongly coupled polarons can be shifted by the spin-orbit interaction.Comment: 11 pages, 5 figure

Global Supply Chains: New Trends in the Context of the Coronavirus Pandemic

The article is dedicated to the new trends emerging in the global supply chain, related to the coronavirus pandemic COVID-19, substantially affected production, transportation and marketing of goods. The authors underline a high risks of initial chain location in China, which sporadically leads to a localization of production supply within national borders. This biase in the international logistics is rather long term than short term I terms of national sustainability. The authors underline the icreasing significance of risk reduction and supply chain reliability over minimization of cost in the logistical decision makings. The ambivalency in the trade of the pandemic emergency goods is analysed in a sense of providing specifically favourable terms for its sirculation among the countries on the one side and the national protection issued for such goods by the national governments, pursuing its sufficient provision on the domestic market on the other side

Modern Challenges for International Sea Freight

The article highlights the new realities in the international freight transportation emerged under the simultaneous challenges, related to the global economic crisis, climate change and the COVID-19 pandemic consequences. The authors argue that the seaborn trade has been encountering a fundamental disorders a long before the contemporary global shocks emergence. Additionally the global container crisis, caused by the shortage of free containers and its growing costs has made the whole situation in the international freight transportation worse, causing the delivery time extention and the growth of inflation. The article is aimed on the identification of the most challenging problems in theory and decision makings, encountering the international freight turnover. Analysing the breakthrough research, expertise and applying the new methodological findings the authors of the articleargue the prospective transformation of the international logistics and proposing new framing features for the global supply chaing configuration. The article states the most undermining processes for the international feight turnover such as the global economic crisis, from its beginning in 2008, the enforcement of the international trade contradictions, specifically US-China trade war, ecological degradation, climate change and the global supply chain disruption, enforced by the global container crisis. The unique role of China as the preconditioning chain in the global supply of the commodities, parts and assembiles was revealed as the most risky factor for the business and governments in all over the world. The article concludes that the global system of international seaborn freight transportation has been entering into the epoch of profound transformation. The foresighting about the main direction of that transformation could be meaningful for Russia and the elaboration of its national transportation strategy

Joule Heating and Current-Induced Instabilities in Magnetic Nanocontacts

We consider the electrical current through a magnetic point contact in the limit of a strong inelastic scattering of electrons. In this limit local Joule heating of the contact region plays a decisive role in determining the transport properties of the point contact. We show that if an applied constant bias voltage exceeds a critical value, the stationary state of the system is unstable, and that periodic, non-harmonic oscillations in time of both the electrical current through the contact and the local temperature in the contact region develop spontaneously. Our estimations show that the necessary experimental conditions for observing such oscillations with characteristic frequencies in the range $10^8 \div 10^9$ Hz can easily be met. We also show a possibility to manipulate upon the magnetization direction of a magnetic grain coupled through a point contact to a bulk ferromagnetic by exciting the above-mentioned thermal-electric oscillations.Comment: 9 pages, 6 figures, submitted to Physical Review

Hydrodynamic Compaction and Sintering of Titanium Filters

This paper describes the development of an equipment for hydrodynamic compaction for production of porous permeable materials and compares the process with the more widely known hydrostatic process. Technical design data, mathematical expressions involved, effect of operating parameters on quality of the sintered product have been discussed

Search for double beta decay of 136^{136}Ce and 138^{138}Ce with HPGe gamma detector

Search for double $\beta$ decay of $^{136}$Ce and $^{138}$Ce was realized with 732 g of deeply purified cerium oxide sample measured over 1900 h with the help of an ultra-low background HPGe $\gamma$ detector with a volume of 465 cm$^3$ at the STELLA facility of the Gran Sasso National Laboratories of the INFN (Italy). New improved half-life limits on double beta processes in the cerium isotopes were set at the level of $\lim T_{1/2}\sim 10^{17}-10^{18}$~yr; many of them are even two orders of magnitude larger than the best previous results.Comment: 21 pages, 6 figures, 3 tables; version accepted for publication on Nucl. Phys.