The possibility of using a vertical array for estimating the delays of sound pulses at multimegameter ranges

The majority of schemes used for acoustic monitoring of temperature fields in the ocean are based on measuring the variations of the so-called ray arrival times, i.e., the travel times of sound pulses along different ray trajectories connecting a source and a receiver. The solution of the inverse problem is considerably hindered by the fact that, in the case of signal detection by a point receiver, it is possible to resolve only the sound pulses propagating along steep rays. To a large extent, this is caused by the phenomenon of ray chaos, which is fully developed at distances of about one thousand of kilometers. The present study shows that the use of a vertical receiving array provides an opportunity to loosen this restriction. An appropriate space-time processing procedure is proposed. The procedure is based on the characteristics of ray arrival distribution in the time-depth plane that remain stable even under the conditions of ray chaos.     

On the possibility of P-violation at finite baryon-number densities

We show how the introduction of a finite baryon density may trigger spontaneous parity violation in the hadronic phase of QCD. Since this involves strong interaction physics in an intermediate energy range we approximate QCD by a σ model that retains the two lowest scalar and pseudoscalar multiplets. We propose a novel mechanism based on interplay between lightest and heavy meson states which cannot be realized solely in the Goldstone boson (pion) sector and thereby is unrelated to the one advocated by Migdal some time ago. Our approach is relevant for dense matter in an intermediate regime of few nuclear densities where quark percolation does not yet play a significant role.     

Comments on the possibility of electroweak baryon number violation at high temperatures

Anomalous baryon number violation in the standard electroweak theory was first discussed by 't Hooft, who found it to be suppressed by a large factor exp(−8π²/g²) at zero temperature, due to a large energy barrier separating vacua with different baryon number. One might have expected that in the early Universe or in high-energy collisions, this process would become unsuppressed when the energies involved became comparable to the barrier height. We argue here that in both cases processes violating baryon number are likely to remain suppressed by a least the same zero-temperature factor.     

Flow-induced noise of a wall-mounted finite airfoil at low-to-moderate Reynolds number

This paper presents an experimental investigation of the flow-induced noise created by a wall-mounted finite airfoil at low-to-moderate Reynolds number and zero angle of attack. Far-field noise measurements have been taken at a single observer location and with two perpendicular microphone arrays in an anechoic wind tunnel at Reynolds numbers of _Rec=9.2×10⁴–1.6×10⁵${\mathit{Re}}_c=9.2\times {10}^4–1.6\times {10}^5$, based on chord, and for a variety of airfoil aspect ratios (length to chord ratio of L/C=0.2–2$L/C=0.2–2$, corresponding to length to thickness ratio of L/T=1.7–16.7$L/T=1.7–16.7$). Additionally, surface oil-film visualisation images and unsteady velocity measurements taken in the near trailing edge wake are related to far-field noise measurements to determine the flow mechanisms responsible for noise generation. The results show that the wall-mounted finite airfoil radiates noise similar to a two-dimensional airfoil when L/T>8.3$L/T>8.3$. Despite the incoming boundary layer height at the junction being 1.30≤δ/T≤1.46$1.30\le \delta /T\le 1.46$, junction and tip flow suppresses tonal noise production for airfoil?s up to L/T=8.3$L/T=8.3$ at _Rec=9.2×10⁴–1.2×10⁵${\mathit{Re}}_c=9.2\times {10}^4–1.2\times {10}^5$. Trailing edge noise is found to be the dominant airfoil noise generation mechanism at frequencies above 1 kHz with the position of the noise source along the trailing edge determined by the proportion of the airfoil span influenced by flow at the airfoil–wall junction.     

Percolation transition in Yang-Mills matter at a finite number of colors

We examine baryonic matter at a quark chemical potential of the order of the confinement scale μ(q)～Λ(QCD). In this regime, quarks are supposed to be confined but baryons are close to the "tightly packed limit" where they nearly overlap in configuration space. We show that this system will exhibit a percolation phase transition when varied in the number of colors N(c): at high N(c), large distance correlations at the quark level are possible even if the quarks are essentially confined. At low N(c), this does not happen. We discuss the relevance of this for dense nuclear matter, and argue that our results suggest a new "phase transition," varying N(c) at constant μ(q).     

Possibility of estimating the diffusion coefficient of a medium from series of observations at several points

A possible approach for estimating the diffusion coefficient in a medium from time series of observations at several points is discussed. The approach is based on analyzing how the largest eigenvalue of the covariation matrix depends on the diffusion coefficient. It is shown that for a wide range of systems this dependence is monotonic and may be considered to be a characteristic of the medium. An analysis is made of the boundary conditions for which monotonicity exists. Zh. Tekh. Fiz. 67, 127–130 (November 1997)     

The measurement statistics interpretation of quantum mechanics: Possible values and possible measurement results of physical quantities

Starting with the Born interpretation of quantum mechanics, we show that the quantum theory of measurement, supplemented by the strong law of large numbers, leads to a measurement statistics interpretation of quantum mechanics. A probabilistic characterization of the spectrum of a physical quantity is given, and an analysis of the notions of possible values and possible measurement results is carried out.     

Derivation of a simple coordination number model using a given equation of state and the effective pair potential function

In this work, a simple coordination number (C.N.) model for the (9, 3) Lennard–Jones (LJ) fluid is obtained. It is based on the comparison of the internal pressure derived from a given equation of state (EoS) with the internal pressure derived from the (9, 3) LJ fluid as an effective pair potential (EPP). This model reproduces well the thermodynamic properties of the fluid such as internal energy, and the C.N. which is comparable with the Monte Carlo simulation data for the C.N. in the high-density region. In addition, the obtained C.N. can predict the first shell radial distribution function, g(r), of the fluid as well.     

Does the flatness of the velocity derivative blow up at a finite Reynolds number?

A tentative suggestion is made that the flatness of the velocity derivative could reach an infinite value at finite (though very large) Reynolds number, with possible implications for the singularities of the Navier—Stokes equations. A direct test of this suggestion requires measurements at Reynolds numbers presently outside the experimental capacity, so an alternative suggestion that can be tested at accessible Reynolds numbers is also made.     

On the possibility of obtaining a finite value for the proton-neutron mass difference

We discuss the possibility of evaluating the p-n mass difference unambiguously, taking in account a possible violation of Bjorken scaling law in the deep inelastic e-p, e-n scattering. We find that even a very small amount of violation is sufficient in order to obtain the correct value for the p-n mass difference.     

The differential characteristics of control rods of VVER-1000 core simulator at a low number of axial mesh points

An algorithm for refining the differential characteristics of the control rods (CRs) of the control and protection system (CPS) for a neutronics model of the VVER-1000 simulator at a low number of axial mesh points of the core is described. The problem of determining the constants for a cell with a partially inserted CR is solved. The cell constants obtained using the proposed approach ensure smoothing of the differential characteristics of an absorbing rod. The algorithm was used in the VVER-1000 simulators (Bushehr NPP, unit no. 1; Rostov NPP, unit no. 1; and Balakovo NPP, unit no. 4).     

Single-particle distribution function of a quantum dot system at finite temperature

In the present paper, we shall rigorously re-establish the result of the single-particle function of a quantum dot system at finite temperature. Unlike the proof given in our previous work (Phys. Rev. B 74 195414 (2006)), we take a different approach, which does not exploit the explicit expression of the Gibbs distribution function. Instead, we only assume that the statistical distribution function of the quantum dot system is thermodynamically stable. As a result, we are able to show clearly that the electronic structure in the quantum dot system is completely determined by its thermodynamic stability. Furthermore, the weaker requirements on the statistical distribution function also make it possible to apply the same method to the quantum dot systems in non-equilibrium states.     

Single-particle distribution function of a quantum dot system at finite temperature

In the present paper,we shall rigorously re-establish the result of the single-particle function of a quantum dot system at finite temperature.Unlike the proof given in our previous work(Phys.Rev.B 74 195414(2006)),we take a different approach,which does not exploit the explicit expression of the Gibbs distribution function.Instead,we only assume that the statistical distribution function of the quantum dot system is thermodynamically stable.As a result,we are able to show clearly that the electronic structure in the quantum dot system is completely determined by its thermodynamic stability.Furthermore,the weaker requirements on the statistical distribution function also make it possible to apply the same method to the quantum dot systems in non-equilibrium states.     

Moiré fringes as two-dimensional autocorrelation of transmission function of linear gratings and its application for modulation transfer function measurement

In this work, we show that the transmission moiré pattern is two-dimensional autocorrelation of transmission function (2D-ACTF) of two superimposed linear gratings that make a small angle with each other. In this approach, the properties of moiré fringes vs. the relative displacement of the gratings are formulated. By measuring 2D-ACTF of two similar gratings, we evaluate the modulation transfer function (MTF) of the gratings’ generating system. This work is the generalized form of our previous works. The implied MTF measurement method is easier and faster than our previous methods.     

The velocity autocorrelation function of a finite model system

We investigate in detail the dependence of the velocity autocorrelation function of a one-dimensional system of hard, point particles with a simple velocity distribution function (all particles have velocities ±c) on the size of the system. In the thermodynamic limit, when both the number of particlesN and the length of the boxL approach infinity andN/L , the velocity autocorrelation function(t) is given simply by c² exp(–2ct@#@). For a finite system, the function _N(t) is periodic with period 2L/c. We also show that for more general velocity distribution functions (particles can have velocities ±c_i,i = 1,...), _N(t) is an almost periodic function oft. These examples illustrate the role of the thermodynamic limit in nonequilibrium phenomena: We must keept fixed while letting the size of the system become infinite to obtain an auto-correlation function, such as(t), which decays for all times and can be integrated to obtain transport coefficients. For any finite system, our _N (t) will be very close to(t) as long ast is small compared to the effective size of the system, which is 2L/c for the first model.Supported in part by the AFOSR under Contract No. F44620-71-C-0013.     

Universal adaptive lattice filters. Adaptation for a given root of the estimating correlation matrix

Algorithms for the adjustment of adaptive lattice filters according to a given root of the estimating noise-correlation matrix (CM) are considered. A basic algorithm is synthesized from which can be derived adjustment algorithms that take into account a priori information on the CM structure. Methods for simplification of the algorithm and increasing its efficiency are examined.