Extreme driven ion acoustic waves

Excitation of large amplitude strongly nonlinear ion acoustic waves from a trivial equilibrium by a chirped frequency drive is discussed. Under certain conditions, after passage through the linear resonance in this system, the nonlinearity and the variation of parameters work in tandem to preserve the phase-locking with the driving wave via excursion of the excited ion acoustic wave in its parameter space, yielding controlled growth of the wave amplitude. We study these autoresonant waves via a fully nonlinear warm fluid model and predict formation of sharply peaked (extreme) ion acoustic excitations with local ion density significantly exceeding the unperturbed plasma density. The driven wave amplitude is bounded by the kinetic wave-breaking, as the local maximum fluid velocity of the wave approaches the phase velocity of the drive. The Vlasov-Poisson simulations are used to confirm the results of the fluid model and the Whitham's averaged variational principle is applied in analyzing evolution of the autoresonant ion acoustic waves

Excitation and control of large amplitude standing magnetization waves

A robust approach to excitation and control of large amplitude standing magnetization waves in an easy axis ferromagnetic by starting from a ground state and passage through resonances with chirped frequency microwave or spin torque drives is proposed. The formation of these waves involves two stages, where in the first stage, a spatially uniform, precessing magnetization is created via passage through a resonance followed by a self-phase-locking (autoresonance) with a constant amplitude drive. In the second stage, the passage trough an additional resonance with a spatial modulation of the driving amplitude yields transformation of the uniform solution into a doubly phase-locked standing wave, whose amplitude is controlled by the variation of the driving frequency. The stability of this excitation process is analyzed both numerically and via Whitham's averaged variational principle

Autoresonant excitation of Bose-Einstein condensates

Controlling the state of a Bose-Einstein condensate driven by a chirped frequency perturbation in a one-dimensional anharmonic trapping potential is discussed. By identifying four characteristic time scales in this chirped-driven problem, three dimensionless parameters $P_{1,2,3}$ are defined describing the driving strength, the anharmonicity of the trapping potential, and the strength of the particles interaction, respectively. As the driving frequency passes the linear resonance in the problem, and depending on the location in the $P_{1,2,3}$ parameter space, the system may exhibit two very different evolutions, i.e. the quantum energy ladder climbing (LC) and the classical autoresonance (AR). These regimes are analysed both in theory and simulations with the emphasis on the effect of the interaction parameter $P_{3}$. In particular, the transition thresholds on the driving parameter $P_{1}$ and their width in $P_{1}$ in both the AR and LC regimes are discussed. Different driving protocols are also illustrated, showing efficient control of excitation and de-excitation of the condensate

Resonant control of solitons

It is shown that the effect of "scattering on resonance" can be used to control envelope solitons in the driven nonlinear Schrödinger equation. The control occurs by the frequency modulated driving with multiple crossing of the resonant frequency of the soliton. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved

Quantum versus classical phase-locking transition in a driven-chirped oscillator

Classical and quantum-mechanical phase locking transition in a nonlinear oscillator driven by a chirped frequency perturbation is discussed. Different limits are analyzed in terms of the dimensionless parameters $/\sqrt{2m\hbar \omega_{0}\alpha}$ and $P_{2}=(3\hbar \beta)/(4m\sqrt{\alpha})$ ($\epsilon,$ $\alpha,$ $\beta$ and $\omega_{0}$ being the driving amplitude, the frequency chirp rate, the nonlinearity parameter and the linear frequency of the oscillator). It is shown that for $P_{2}\ll P_{1}+1$, the passage through the linear resonance for $P_{1}$ above a threshold yields classical autoresonance (AR) in the system, even when starting in a quantum ground state. In contrast, for $$, the transition involves quantum-mechanical energy ladder climbing (LC). The threshold for the phase-locking transition and its width in $P_{1}$ in both AR and LC limits are calculated. The theoretical results are tested by solving the Schrodinger equation in the energy basis and illustrated via the Wigner function in phase space

The interaction of grassroots communities and local authorities in Russia

Taking into consideration the underdevelopment of the Russian civil community it is of essential interest to touch upon local communities (known as TOS). Local governments and TOS communities could provide similar services and as such cooperate or compete with each other. Community initiatives could supplant poorly performing government services, or governments could outsource to communities some of its functions. Based on empirical Russian data, collected in the city of Kirov this research shows that the prevailing initial incentive to establish TOS is driven by the prospect of obtaining seed money from the government. We detected sources of TOS advantages over municipal authorities: ratio of costs and benefits, sensitivity to the demands of consumers, social capital, and voluntary nature of TOS. TOS are more likely to emerge in communities where people are sceptical about the efficacy of conventional mechanisms of democratic accountability, and prefer to collaborate with municipal governments on specific project

The interaction of grassroots communities and local authorities in Russia

Taking into consideration the underdevelopment of the Russian civil community it is of essential interest to touch upon local communities (known as TOS). Local governments and TOS communities could provide similar services and as such cooperate or compete with each other. Community initiatives could supplant poorly performing government services, or governments could outsource to communities some of its functions. Based on empirical Russian data, collected in the city of Kirov this research shows that the prevailing initial incentive to establish TOS is driven by the prospect of obtaining seed money from the government. We detected sources of TOS advantages over municipal authorities: ratio of costs and benefits, sensitivity to the demands of consumers, social capital, and voluntary nature of TOS. TOS are more likely to emerge in communities where people are sceptical about the efficacy of conventional mechanisms of democratic accountability, and prefer to collaborate with municipal governments on specific project

Dag Hammarskjold and concept formation of peacemaking operations

© Medwell Journals, 2015. Actuality of the problem to be investigated depends on the circumstances that the armed conflicts have become widespread in the modern world. To settle up them the UNO carries out the peacemaking operations and the study of the process of formatting the peacemaking operation concept provides today an optimal policy of its fulfillment. The study aims at investigating the formation process of the concept of the peacemaking operations and the role of the Secretary General of the United Nations D. Hammarskjold there. The study deals with the formation process of the concept of peacemaking operations major contribution to which was made by the second UN Secretary General Dag Hammarskjold who was holding the post in the period of the years 1953-1961. The researcher considers, the attempts of forming international armed forces for the response to threatening to international peace and security. By way of the example of settlement of the conflicts in the Middle-East and the Congo the basic principles of peacemaking concept of Hammarskjöld are stated. The materials of the study may be useful in the process of discussion of a possible concept reformation of peacemaking operations of the UNO

Regional problems in the North-East Africa

This paper deals with the analysis of the regional security problems in the North-East Africa. The author refers in the introduction to the colonial past of the African continent, when the territory of African countries was arbitrarily divided between the major colonial powers. After the Second World War as a result of raising the national liberation movement the African peoples gained independence, but the colonial past has left its imprint on the new independent states in the form of a series of armed conflicts, upon which the author dwells in the main part. The author pays major attention to the conflicts in the North-East Africa, particularly, in the Horn of Africa. The author exhaustively covers the main causes of African conflicts such as the colonial past of these countries, arbitrarily set boundaries, as a result of which many of African nations were divided, as well as difficult post-colonial national-state development, and the active intervention of external forces. The conflicts in Somalia, Sudan, inter-state conflicts between Ethiopia and Somalia and between Ethiopia and Eritrea have been considered. There have been distinguished regional and international organizations, which in prospect should assume the responsibility for the maintenance of regional security.peer-reviewe