Observation of nonlinear evolution of acoustic pulses in the absence of diffraction
Observation of nonlinear evolution of acoustic pulses in the absence of diffraction
A.N. Dubrovskii, 0.A. Sapozhnikov
The results of experiments are discussed in which a nonlinear evolution of acoustic pulses was observed under specially chosen conditions, where the effect of diffraction was practically ruled out. Acoustic pulses were generated by an optoacoustic method, which enables one to obtain short powerful pulses of predictable shape. The pulses were picked up by a hydrophone based on a polyvinylidene fluoride film. At high peak pressures the evolution of an almost triangular profile with a clearly pronounced discontinuous front was observed. The pulse amplitude decreased in inverse proportion to the root of the distance to the radiator. The experimental results are in good agreement with the classical theory of such waves.
Show AbstractCharacteristic solutions of Takagi equations in two-ray dynamic diffraction
Characteristic solutions of Takagi equations in two-ray dynamic diffraction
A.V. Kolpakov, I.R. Prudnikov
The earlier introduced representation of characteristic solutions of the Takagi equations in the two-ray dynamic diffraction is further developed by the authors. It is shown that this approach is physically adequate to the concept of a dynamically self-consistent system of fields in a crystal. Within the framework of this approach, equations are derived for characteristic solutions in a perfect and in a one-dimensionally distorted crystal. It is demonstrated that the system of Takagi equations involving a local accommodation function is singled out in the consideration of diffraction by one-dimensionally distorted crystals. Based on the notion of characteristic solutions of the Takagi equations, a model of a crystal with random one-dimensional distortion field is considered and the statistical averaging of the equations for characteristic solutions is carried out.
Show AbstractStructural and magnetic properties of nickel films deposited from oscillating-electron discharge under low-energy krypton ion irradiation
Structural and magnetic properties of nickel films deposited from oscillating-electron discharge under low-energy krypton ion irradiation
G.V. Smirnitskaya, S.V. Sveshnikov, L.V. Nikitin, D.M. Gazdiev, E.V. Likhushina, L.S. Mironova, T.I. Udilina
Tl1e structural and magnetic parameters of Ni films obtained from a discharge with oscillating electrons are shown to depend on the energy of $Кr^+$ ions bombarding the film in the course of deposition. The shape of the energy dependence is explained by several factors, including the presence of discrete ionization regions in the discharge, the elastic and inelastic interactions of $Кr^+$ ions with the film surface, the ratio of fluxes of Ni atoms and $Кr^+$ ions in the two discharge regimes studied, and the difference in the character of ion interaction with the fee and hep phases of nickel.
Show AbstractDirect detection of inhomogeneous short-range order in the Al-Cu (0.5 at.%) alloy
Direct detection of inhomogeneous short-range order in the Al-Cu (0.5 at.%) alloy
V.M. Silonov, B.T. Bokebaev, E.V. Evlyukhina
It has been shown by the technique of X-ray diffuse scattering that in the AlCu (0.5 at.%) alloy immediately after its preparation there is inhomogeneous short-range order.
Show AbstractMeasurement of short lifetimes of minority charge carriers in silicon solar cells irradiated by fast electrons
Measurement of short lifetimes of minority charge carriers in silicon solar cells irradiated by fast electrons
0.G. Koshelev, V.A. Morozova, E.Yu. Barinova, G.M. Grigor'eva, E.M. Tkacheva
A new modulation method was suggested to determine short lifetimes $(\ge10^{-8} с)$ of minority charge carriers in the base region of solar cells. The method is based on compensation for the alternating photocurrent by an additional current source. Data obtained for single-crystal silicon solar cells irradiated by a fluence of electrons (below $10^{16} см^{-2}$) with 1 MeV energy are presented.
Show AbstractW-boson pair production with undetected electrons - a new basic process for $\gamma e$ colliders
W-boson pair production with undetected electrons - a new basic process for $\gamma e$ colliders
I.F. Ginzburg$^1$, V.A. Il'in$^2$, A.E. Pukhov$^2$, V.G. Serbo$^3$
The total cross section of the process $\gamma e\to eWW$ at energies up to 2 TeV has been calculated. The contributions to the process come from the three- and fourboson vertices ($\gamma WW$, $ZWW$, $\gamma \gamma WW$ and $\gamma ZWW$). The large magnitude of the cross section suggests that this will be one of the most interesting processes in studying the structure of the electroweak sector of the Standard Model using the linear colliders that are now being designed.
Show AbstractFocusing of weak acoustic pulses
Focusing of weak acoustic pulses
A.G. Musatov, 0.A. Sapozhnikov
The process of focusing of acoustic pulses is investigated theoretically and experimentally. The analysis is carried out in the parabolic approximation. It is shown that the pulse profile at an arbitrary point of a Gaussian beam can be found using Green's function. The calculation of the acoustic field is performed for different focusing conditions. The numerical results are in good agreement with the experimental data. The proposed approach makes it possible to calculate pulse acoustic fields sufficiently accurately and take account of the effects of focusing and diffraction.
Show AbstractOn a possibility of acoustic matching for hydroacoustic transducers of small wave size
On a possibility of acoustic matching for hydroacoustic transducers of small wave size
P.N. Kravchun
The problem of one-frequency matching of complex impedances with the help of an acoustic lumped-parameter matching system is considered. The solution is illustrated by calculations of matching systems for hydroacoustic transducers of small wave size. The properties of matching systems and the possibilities of their optimization are discussed.
Show AbstractNumerical modeling of the tsunami generation process by a landslide on a sloping sea floor
Numerical modeling of the tsunami generation process by a landslide on a sloping sea floor
O.V. Kostitsyna
A numerical method is used to study the possibility and efficiency of tsunami generation. by an underwater landslide. The effect of the rate and travel distance of the landslide on characteristics of the wave it generates is considered at slope angles within 0-0.06 rad corresponding to actual slopes of the sea floor. It is shown that the dependence of the energy and amplitudes of the waves on the rate of the landslide are of resonance nature, and that the position of the resonance region depends on the landslide travel distance both for a horizontal and a sloping sea floor.
Show AbstractOn the theory of frequency dependence of conductivity in disordered organic semiconductors
On the theory of frequency dependence of conductivity in disordered organic semiconductors
I.P. Zvyagin, V.P. Petrova
A phononless contribution to low-temperature alternating-current conductivity for a model with a diagonal disorder is calculated with consideration for quantum correlation of the levels. It is shown that a band corresponding to resonance transitions between neighboring-localized states can appear in the IR absorption spectra of organic semiconductors.
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