Wave attenuation model for dephasing and measurement of conditional times

Inelastic scattering induces dephasing in mesoscopic systems. An analysis of previous models to simulate inelastic scattering in such systems is presented and a relatively new model based on wave attenuation is introduced. The problem of Aharonov-Bohm (AB) oscillations in conductance of a mesoscopic ring is studied. We show that the conductance is symmetric under flux reversal and the visibility of AB oscillations decays to zero as a function of the incoherence parameter, signaling dephasing. Further the wave attenuation model is applied to a fundamental problem in quantum mechanics, that of the conditional (reflection/transmission) times spent in a given region of space by a quantum particle before scattering off from that region.     

Solid-phase spectrophotometric analysis of natural water with the simultaneous sample preparation and dynamic preconcentration of test components on reagent cellulose matrices

A photocolorimeter was developed; this instrument made it possible to perform sample preparation, to preconcentrate test water components on indicator cellulose matrices, and to simultaneously measure their light absorption. A white light-emitting diode and a Digital color sensor S9706 photodiode, which simultaneously detected red (615 nm), green (540 nm), and blue (465 nm) regions of the spectrum, were used in the instrument. The applicability of the photocolorimeter to the determination of 36 components and characteristics of water was demonstrated. The photocolorimeter was proposed for the simultaneous determination of 20 components at a level of their maximum permissible concentrations for fishery water (RSD < 10%) for 10–15 min.     

Lunar orbital radio detector and detection potential of ultrahigh-energy particles

The problems of ultrahigh-energy cosmic ray and neutrino detection are considered. It is shown that the radio method is most promising for detecting particles with the highest energies in the Nature. The concept of the LORD experiment is proposed, in which a radio wave detector is installed aboard a circumlunar satellite. The structure and operating principle of this instrument are described. Based on an analytical approach and Monte Carlo simulation, a high scientific potential of the LORD experiment is demonstrated, whose capability to detect particles with limiting energies is much higher than that of all currently existing systems.     

On Conditions for <Emphasis Type="Italic">L</Emphasis><Superscript>2</Superscript>-Dissipativity of Linearized Explicit QGD Finite-Difference Schemes for One-Dimensional Gas Dynamics Equations

An explicit two-level in time and spatially symmetric finite-difference scheme approximating the 1D quasi-gasdynamic system of equations is studied. The scheme is linearized about a constant solution, and new necessary and sufficient conditions for the L²-dissipativity of solutions to the Cauchy problem are derived, including, for the first time, the case of a nonzero background velocity and depending on the Mach number. It is shown that the condition on the Courant number can be made independent of the Mach number. The results provide a substantial development of the well-known stability analysis of the linearized Lax–Wendroff scheme.     

Diagnostics of residual stress in metals with wideband surface acoustic pulses

A method for diagnostics of biaxial residual stress in metals with the use of short pulses of surface acoustic waves (SAWs) is discussed. Laser thermoelastic excitation of SAW pulses with a length of about 30 ns and piezoelectric detection by a specially designed wedgelike receiver with a high time resolution are used. Relative variations in the phase and group SAW velocities due to the presence of a weld are measured experimentally in two mutually perpendicular directions. The frequency range of measurements was 5–25 MHz, which corresponds to a depth of SAW penetration of about 120–600 μm. Measurements were conducted on samples made of 12X18H10T stainless steel with planar dimensions of 105 × 76 mm and thickness h = 8 mm, which were welded along the axis by an electron beam. The weld width was 5–7 mm. After the measurements, the samples were investigated by the fracture method based on the technique of a complete relief. The results of measurements are compared with the data obtained by fracture tests. The potential of the studied method is analyzed, and the measurement errors are estimated.     

On the neutral stability of a shock wave in real media

The results of the theoretical analysis and computer simulation of the behavior of neutrally stable shock waves with real (van der Waals gas, magnesium) equations of state are presented. An approach is developed in which the region of the neutral stability of a shock wave for each pressure value in front of the wave is determined from the analysis of the equation of state. A simple algorithm is developed to determine the cause of acoustic perturbations (a shock front or an external source) immediately from the flow pattern. In contrast to the predictions of the linear theory, the amplitude of the perturbations of the neutrally stable shock wave decreases with time, although this process is noticeably slower than in the case of an absolutely stable shock wave.     

On L2-Dissipativity of a Linearized Explicit Finite-Difference Scheme with Quasi-Gasdynamic Regularization for the Barotropic Gas Dynamics System of Equations

Doklady Mathematics - We study an explicit two-level symmetric (in space) finite-difference scheme for the multidimensional barotropic gas dynamics system of equations with quasi-gasdynamic...