Dynamic Stability of a Composite Circular Cylindrical Shell Subjected to Combined Axial and Torsional Loading

The dynamic stability of thin, clamped, composite circular cylindrical shells is studied for combined axial and torsional loading. Each load is taken to be har monically varying; the frequencies of the two loads differ, in general. For the case in which the frequencies are commensurate, the applied load function is periodic. The equa tions of motion for the shell are reduced to a system of Hill equations by means of Fourier series expansions. Instability regions of principal and combination parametric resonance are determined by use of the monodromy matrix. Numerical results are generated for boron-epoxy layered shells for various cases of pure axial, pure torsional, and combined loading. The width of the principal instability region is presented as a function of fiber ori entation for a laminate case. Stability diagrams are presented covering about 6 times the lowest natural frequency for various ratios of the applied axial and torsional frequencies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66879/2/10.1177_002199839302701802.pd

Stochastic resonance in nuclear fission

Fission decay of highly excited periodically driven compound nuclei is considered in the framework of Langevin approach. We used residual-time distribution (RTD) as a tool for studying the dynamic features in the presence of periodic perturbation. The structure of RTD essentially depends on the relation between Kramers decay rate and the frequency w of periodic perturbation. In particular, the intensity of the first peak in RTD has a sharp maximum at certain nuclear temperature depending on w. This maximum should be considered as fist-hand manifestation of stochastic resonance in nuclear dynamics

Electromagnetic properties of graphene junctions

A resonant chiral tunneling (CT) across a graphene junction (GJ) induced by an external electromagnetic field (EF) is studied. Modulation of the electron and hole wavefunction phases $\varphi$ by the external EF during the CT processes strongly impacts the CT directional diagram. Therefore the a.c. transport characteristics of GJs depend on the EF polarization and frequency considerably. The GJ shows great promises for various nanoelectronic applications working in the THz diapason.Comment: 4 pages 3 figure

Hetero-association of aromatic molecules in aqueous solution

Knowledge of the physical chemistry of small molecules complexation (the hetero-association) in aqueous solution is increasingly important in view of the rapidly emerging branch of supramolecular chemistry dealing with the formation of heterogeneous polymeric structures having specific functional roles. In this paper, the 50-year history of scientific studies of hetero-association of heterocyclic aromatic molecules in aqueous solution has been reviewed. Some important correlations of structural and thermodynamic parameters of complexation have been reported based on large data-set of hetero-association parameters accumulated to date. The fundamental problem of ‘energetic composition’ of π-stacking is extensively discussed. The review has shown that there are some gaps in our understanding of heteroassociation, which provides a challenge for further studies in this are

Status of the Novosibirsk terahertz FEL

The first stage of Novosibirsk high-power free-electron laser (FEL) was commissioned in 2003. It is based on a normal conducting CW energy recovery linac. Now the FEL provides electromagnetic radiation in the wavelength range of 120…180 micrometers. An average power is 400 W. The minimum measured line width is 0.3%, which is close to the Fourier-transform limit. A user-beamline assembly is in progress, parts of the full-scale machine are manufactured. The latter will operate in the near IR region and provide higher average powerВ 2003 году в Новосибирске заработала первая очередь мощного лазера на свободных электронах (ЛСЭ). Машина построена на базе линака-рекуператора непрерывного действия. В настоящее время ЛСЭ работает в диапазоне длин волн 120…180 мкм, его средняя мощность достигает 400 Вт. Минимальная измеренная ши- рина полосы излучения составляет 0.3%, что близко к теоретическому минимуму. В настоящее время монтируются каналы разводки излучения для пользователей, части полномасштабной машины запущены в производство. Полномасштабная машина будет работать в ближнем ИК-диапазоне и обладать большей мощностью.В 2003 році в Новосибірську заробила перша черга потужного лазера на вільних електронах (ЛВЕ). Машина побудована на базі лінака-рекуператора безперервної дії. Зараз ЛВЕ працює в діапазоні довжин хвиль 120...180 мкм, його середня потужність досягає 400 Вт. Мінімальна виміряна ширина смуги випромінювання становить 0.3%, що близько до теоретичного мінімуму. Зараз монтуються канали розведення випромінювання для користувачів, частини повномасштабної машини запущені у виробництво. Повномасштабна машина буде працювати в ближньому ІЧ-діапазоні і мати більшу потужність

Foliations of Isonergy Surfaces and Singularities of Curves

It is well known that changes in the Liouville foliations of the isoenergy surfaces of an integrable system imply that the bifurcation set has singularities at the corresponding energy level. We formulate certain genericity assumptions for two degrees of freedom integrable systems and we prove the opposite statement: the essential critical points of the bifurcation set appear only if the Liouville foliations of the isoenergy surfaces change at the corresponding energy levels. Along the proof, we give full classification of the structure of the isoenergy surfaces near the critical set under our genericity assumptions and we give their complete list using Fomenko graphs. This may be viewed as a step towards completing the Smale program for relating the energy surfaces foliation structure to singularities of the momentum mappings for non-degenerate integrable two degrees of freedom systems.Comment: 30 pages, 19 figure