Free oscillations of the generalized maxwell solid body

Conclusions The free oscillations of the generalized Maxwell body contain a single harmonic and do not contain aperiodic terms. At high temperatures the internal friction tends to a limiting value which depends only on the exponent m.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 165–166, May, 1972.     

Free oscillations of magnetic fluid in strong magnetic field

The paper presents the esults of measuring the elastic parameters of an oscillatory system (coefficient of pondermotive elasticity, damping factor, and oscillation frequency) whose viscous inertial element is represented by a magnetic fluid confined in a tube by magnetic levitation in a strong magnetic field. The role of elasticity is played by the pondermotive force acting on thin layers at the upper and lower ends of the fluid column. It is shown that, by measuring the elastic oscillation frequencies of the magnetic fluid column, it is possible to develop a fundamentally new absolute method for determining the saturation magnetization of a magnetic colloid.     

Free magnetization oscillations in garnet ferrite films with quasi-planar anisotropy

Free magnetization oscillations in garnet ferrite films with quasi-planar anisotropy was studied. The oscillations were excited by a pulse of an in-plane magnetic field. An analytic expression relating the oscillation frequency to the film parameters and the external magnetic field was derived; the expression is in good agreement with the experimental data. The planar anisotropy is shown to increase the free-oscillation damping.     

Transverse oscillations of a long-pulse electron beam on alaser-formed channel

An intense relativistic electron beam may be transported in low-pressure gas using an ion channel which focuses and guides the beam. The beam can be unstable to the growth of transverse oscillations caused by the electric force between the beam and channel-the ion hose instability. Beam propagation on channels created by photoionization of gas with an excimer laser is discussed. Ion hose oscillations have been recorded which have a betatron wavelength of approximately 1.5 m. The growth rate of the ion hose instability in the linear regime was measured as 1.67±0.45. At this level of growth, the amplitude of beam oscillations equals the channel radius after a period of one-third of an ion oscillation time     

Free field oscillations and anomalous wave-scattering conditions in one-dimensionally periodic gratings

Conclusions We have analyzed the relationship between anomalous wave-scattering conditions in a grating of simple model geometry and the excitation of almost-free field oscillations in the structure. The conclusions can be generalized to other gratings whose geometry is such as to permit the identification of coupling channels between the transmission and reflection zones, in which the conditions for the onset of propagating waves are known (this applies to the majority of gratings used in practice). There can be several channels (in one period) or, when they operate asynchronously (i.e., are not exactly identical), the first and second spectral families of free field oscillations can be formed by virtue of the interference summation of waves of the same mode propagating in different channels. The principal family in this case is the one whose spectral lines converge in the limit to a cutoff point that is large in absolute value, but is still responsible for the occurrence of total wave reflection by semitransparent structures [5].The correspondence established between the spectral and anomalous diffraction characteristics demonstrates the resonant nature of the total-transmission and total-reflection conditions; it also make it possible to explain the distinctive features of their onset and to predict with sufficient reliability the likelihood of their occurrence with predetermined parameters. All the corresponding data can be obtained by analysis of the spectral lines describing the dynamics of the variation of the complex eigenfrequencies of the grating.Institute of Radiophysics and Electronics, Academy of Sciences of the Ukrainian SSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 31, No. 3, pp. 312–320, March, 1988.     

Vectorlike weak currents,massive neutrinos,and neutrino beam oscillations

If the weak currents are vectorlike, the neutrinos will not be massless, and there will exist weak mixing angles for leptons, analogous to the Cabibbo angle for hadrons. Neutrino beams will oscillate in a similar way as K_o-beams. The failure to observe a solar neutrino flux at the theoretically predicted rate can be interpreted as the consequence of these oscillations.     

Free vibration behaviour of multiphase and layered magneto-electro-elastic beam

Free vibration studies of multiphase and layered magneto-electro-elastic beam for BaTiO₃–CoFe₂O₄ composite is carried out. In-plane plate finite-element analysis is used to obtain the behaviour of magneto-electro-elastic beam. Studies are carried out for beams for different boundary conditions, as may be applicable in design of smart sensors/actuators. The ANSYS package is used to validate the results obtained by the computer code developed for piezoelectric (PE) beam. Plane stress condition is used for the Euler–Bernouli magneto-electro-elastic beam.     

Measurement of neutrino oscillations with the MINOS detectors in the NuMI beam

This Letter reports new results from the MINOS experiment based on a two-year exposure to muon neutrinos from the Fermilab NuMI beam. Our data are consistent with quantum-mechanical oscillations of neutrino flavor with mass splitting |Deltam2| = (2.43+/-0.13) x 10(-3) eV2 (68% C.L.) and mixing angle sin2(2theta) > 0.90 (90% C.L.). Our data disfavor two alternative explanations for the disappearance of neutrinos in flight: namely, neutrino decays into lighter particles and quantum decoherence of neutrinos, at the 3.7 and 5.7 standard-deviation levels, respectively.     

Increase of probe beam light-induced polarization rotation via accumulation of coherent oscillations

We study possibilities of the method of accumulation of the coherent-nonstationary response of the medium for amplifying the polarization rotation of probe radiation in conditions of a cascade two-photon resonance. The probe field couples the ground level nS _1/2 of an alkali metal atom with the excited doublet nP _1/2,3/2, while the monochromatic pump field couples this doublet with a higher excited state n’S _1/2. We obtain analytic expression for the rotated component of the probe field polarization. It is shown that consistent switching by π the phase of the input probe field may create in the tail portion of its rotated component a separate light pulse with more than an order of magnitude higher intensity, which is a desired result for polarization laser spectroscopy.     

Free vibrations of a laminated beam by a microstructure theory

The free vibrations of a laminated beam are considered within the framework of a theory that models the composite beam as a macrohomogeneous beam with microstructure. The beams are assumed to consist of several parallel alternating layers of two homogeneous, isotropic elastic materials. The system of three coupled partial differential equations is solved exactly, and attention is devoted to the determination of natural frequencies of vibration of laminated beams with (i) hinged-hinged ends and (ii) clamped-clamped ends. For the sake of comparison, the same boundary value problems are also solved within the framework of the so-called effective modulus theory, which treats the composite as a transversely isotropic and “fictitiously” homogeneous Timoshenko beam, with effective moduli and density. For relatively long beams, i.e., in the low frequency range, the natural frequencies obtained from the two theories are in excellent agreement, but as the depth-to-length ratio, ζ, increases the microstructure frequencies are observed to be much lower than the effective modulus frequencies, the magnitude of the effect becoming more pronounced with increasing mode number n.     

The neutralization by ions and a type of oscillations of the electron beam

The neutralization factor is deduced for a partly compensated electron beam in a longitudinal magnetic field. The neutralization factor depends on macroscopic quantities and can be computed for a given configuration. This is used in the dispersion relation and the frequency of self-excited oscillations of the two-stream instability of rotating nonneutral electron-ion beam is found. This frequency modulates the electron beam current. The existence of such oscillations is proved experimentally and the used experimental technique is described.     

Free vibration analysis of a cracked beam by finite element method

In this paper, the natural frequencies and mode shapes of a cracked beam are obtained using the finite element method. An ‘overall additional flexibility matrix’, instead of the ‘local additional flexibility matrix’, is added to the flexibility matrix of the corresponding intact beam element to obtain the total flexibility matrix, and therefore the stiffness matrix. Compared with analytical results, the new stiffness matrix obtained using the overall additional flexibility matrix can give more accurate natural frequencies than those resulted from using the local additional flexibility matrix. All the elements in the overall additional flexibility matrix are computed by 128-point (1D) or (128×128)-point (2D) Gauss quadrature, and then further best fitted using the least-squares method. The explicit form best-fitted formulas agree very well with the numerical integration results, and are very convenient for use and valuable for further reference. In addition, the authors constructed a shape function that can perfectly satisfy the local flexibility conditions at the crack locations, which can give more accurate vibration modes.     

Free electron laser spectral dynamics with a modulation of electron beam energy

Recent experimental and theoretical works on free electron laser spectral dynamics have pointed out the difficulty to obtain a narrow and stable spectrum operation. This goal can only be achieved by avoiding the sideband generation leading to a broadband and unstable spectrum. Tapered wiggler and two-frequency wiggler are well suited for combining sharp spectrum and high efficiency but are not really compatible with a wide tunability of laser light. Filtering sidebands is a good way for lower power experiments but it seems to be difficult to conceive wideband filters, specially in the far-infrared region. Modulation of electron energy is a new potential soft way for controlling the spectral dynamics of longpulse free electron laser. Spectral dynamics under the modulation is investigated in the linear and non-linear regimes in the far-infrared region. Simulations show that a pulsed and sharp spectrum behavior can be obtained by optimizing the modulation parameters. The interest of such a method for the far-infrared experiments is discussed.     

Free vibration analysis of a uniform multi-span beam carrying multiple spring-mass systems

The literature regarding the free vibration analysis of single-span beams carrying a number of spring-mass systems is plenty, but that of multi-span beams carrying multiple spring-mass systems is fewer. Thus, this paper aims at determining the “exact” solutions for the natural frequencies and mode shapes of a uniform multi-span beam carrying multiple spring-mass systems. Firstly, the coefficient matrices for an intermediate pinned support, an intermediate spring-mass system, left-end support and right-end support of a uniform beam are derived. Next, the numerical assembly technique for the conventional finite element method is used to establish the overall coefficient matrix for the whole vibrating system. Finally, equating the last overall coefficient matrix to zero one determines the natural frequencies of the vibrating system and substituting the corresponding values of integration constants into the related eigenfunctions one determines the associated mode shapes. In this paper, the natural frequencies and associated mode shapes of the vibrating system are obtained directly from the differential equation of motion of the continuous beam and no other assumptions are made, thus, the last solutions are the exact ones. The effects of attached spring-mass systems on the free vibration characteristics of the 1-4-span beams are studied.