Showing papers by "Moscow Institute of Physics and Technology published in 2004"
TL;DR: In this article, the spatial uniformity of combustion in a gas mixture initiated by a high-voltage nanosecond volume discharge has been investigated at gas pressures of 03-24 atm and temperatures of 1100-2250 K.
135 citations
TL;DR: In this paper, the main regimes of interaction of relativistically strong electromagnetic waves with plasma under conditions in which the radiation from particles plays a dominant role are discussed, and an approach is developed for generating superintense electromagnetic pulses by means of up-to-date laser devices.
Abstract: A study is made of the main regimes of interaction of relativistically strong electromagnetic waves with plasma under conditions in which the radiation from particles plays a dominant role. The discussion is focused on such issues as the generation of short electromagnetic pulses in the interaction of laser light with clusters and highly efficient ion acceleration in a thin plasma slab under the action of the ponderomotive pressure of the wave. An approach is developed for generating superintense electromagnetic pulses by means of up-to-date laser devices.
134 citations
TL;DR: A microscopic theory of spatial–temporal congested traffic patterns in heterogeneous traffic flow with a variety of driver behavioural characteristics and vehicle parameters is presented.
Abstract: A microscopic theory of spatial–temporal congested traffic patterns in heterogeneous traffic flow with a variety of driver behavioural characteristics and vehicle parameters is presented. A microscopic model for heterogeneous traffic flow is developed based on three-phase traffic theory. Diverse congested pattern features at a freeway bottleneck due to an on-ramp in heterogeneous traffic flow on a two-lane freeway are found. A numerical study of these specific pattern features and their comparison with empirical results are performed. A comparison of congested patterns in heterogeneous traffic flow with congested patterns in traffic flow with identical vehicles is made.
79 citations
TL;DR: Several equivalent formulations of the additivity conjecture for constrained channels, which formally is substantially stronger than the unconstrained additivity, are given in this article, and a characteristic property of the optimal ensemble for such a channel is derived, generalizing the maximal distance property.
Abstract: Several equivalent formulations of the additivity conjecture for constrained channels, which formally is substantially stronger than the unconstrained additivity, are given. To this end a characteristic property of the optimal ensemble for such a channel is derived, generalizing the maximal distance property. It is shown that the additivity conjecture for constrained channels holds true for certain nontrivial classes of channels. After giving an algebraic formulation for Shor’s channel extension, its main asymptotic property is proved. It is then used to show that additivity for two constrained channels can be reduced to the same problem for unconstrained channels, and hence, ‘‘global’’ additivity for channels with arbitrary constraints is equivalent to additivity without constraints.
60 citations
TL;DR: In this paper, the lasing characteristics of a Fe:ZnSe single crystal grown from the vapour phase by the free-growth technique using the chemical transport in hydrogen are studied.
Abstract: The lasing characteristics of a Fe:ZnSe single crystal grown from the vapour phase by the free-growth technique using the chemical transport in hydrogen are studied. A Fe2+:ZnSe laser cooled to liquid nitrogen temperature and pumped by 2.9364-μm radiation from an Er:YAG laser produces the 130-mJ output energy with a slope efficiency of 40% in terms of the absorbed energy, which corresponds to a quantum efficiency of 55%. The lasing spectrum in a dispersive resonator can be continuously tuned between 3.77 and 4.40 μm.
59 citations
05 Jan 2004
53 citations
TL;DR: In this paper, a linear and nonlinear stability analysis of the entropy layer over a blunted plate is discussed, and results of the linear stability theory are compared with the direct numerical solution of the Euler equations when a disturbance of prescribed frequency is imposed on the mean flow.
Abstract: Linear and nonlinear stability analyses of the entropy layer over a blunted plate are discussed. Results of the linear stability theory are compared with the direct numerical solution of the Euler equations when a disturbance of prescribed frequency is imposed on the mean flow. A solver of the Euler equations based on the space-time conservation element/solution element method predicts linear and nonlinear dynamics of unstable disturbances with high accuracy. The nonlinear effect demonstrates a trend to saturation of the entropy-layer disturbances
47 citations
TL;DR: In this paper, the quasistatic electromagnetic density of states for aggregates of touching spheres, in particular, linear chains and computer-generated random fractal aggregates, are calculated.
Abstract: We calculate the quasistatic electromagnetic density of states for aggregates of touching spheres, in particular, linear chains and computer-generated random fractal aggregates. Multipole moments with orders of up to $L=64$ are taken into account for random aggregates with the number of particles of up to $N=100$ and up to $L=8000$ for linear chains. Extensive comparisons with the dipole approximation and geometrical cluster renormalization method are performed. Extinction spectra are calculated for several metals and black carbon. Long wavelength electromagnetic properties of fractal aggregates are considered in details.
47 citations
TL;DR: In this paper, the stagnation dynamics of a cathode-directed streamer discharge in two-dimensional geometry has been studied for the first time, and it has been shown that as the streamer decelerates the radius of the head decreases more rapidly than its potential.
Abstract: The stagnation dynamics of a cathode-directed streamer discharge in two-dimensional geometry has been studied for the first time. It has been shown that as the streamer decelerates the radius of the streamer head decreases more rapidly than its potential, which, in turn, leads to an increase in the maximum electric field as well as an increase in the charged particle densities in the streamer head.
41 citations
TL;DR: In this article, experimental data on the shock compression, temperature, and absorptivity of gaseous deuterium with an initial density close to its value in the liquid state were obtained on a spherical explosion shock-wave generator in a pressure range of 80-90 GPa.
Abstract: Experimental data on the shock compression, temperature, and absorptivity of gaseous deuterium with an initial density close to its value in the liquid state were obtained on a spherical explosion shock-wave generator in a pressure range of 80–90 GPa. The obtained results are compared with the existing experimental and theoretical data.
40 citations
TL;DR: In this article, a frequency dependence of the transfer function of an electrochemical cell is studied experimentally in the frequency span 0.02 to 40 Hz under conditions of controlled convective diffusion.
Abstract: A frequency dependence of the transfer function of an electrochemical cell is studied experimentally in the frequency span 0.02 to 40 Hz under conditions of controlled convective diffusion. Above the diffusion frequency, experimental data nicely conform to theoretical calculations, but below it the function's decay cannot be explained within existing theoretical notions.
20 Sep 2004
TL;DR: This work considers parallel task scheduling problems for hierarchical decentralized systems that consist of homogeneous computational resources such as clusters, PCs and supercomputers, and are geographically dispersed, and focuses on two-level hierarchy scheduling.
Abstract: We consider parallel task scheduling problems for hierarchical decentralized systems that consist of homogeneous computational resources such as clusters, PCs and supercomputers, and are geographically dispersed. We concentrate on two-level hierarchy scheduling: at the first level, the broker allocates computational tasks to the resource. At the second level, each resource schedules the tasks assigned to it using heuristics based, for instance, on strip-packing algorithms. The allocation strategies and efficiency of proposed hierarchical scheduling algorithms are discussed.
TL;DR: In this paper, the frequency response of a diffusion transducer with gauze electrodes, studied theoretically at high frequencies, is proportional to ∼ω-3/2 starting with ω = D/R 2 at ω < ν/R2 and to ∼φ-1 at φ > φ + R 2.
Abstract: The frequency response of a diffusion transducer with gauze electrodes, studied theoretically at high frequencies, is proportional to ∼ω-3/2 starting with ω = D/R
2 at ω < ν/R
2 and to ∼ω-1 at ω > ν/R
2. Here, ω = 2πf, f is the signal frequency, ν the electrolyte viscosity, D a diffusion coefficient, and R the radius of the gauze filaments. The calculation is compared with experiment.
TL;DR: In this paper, the effects of radiation drag force on the structure of relativistic electronpositron and electronproton outflows were considered within the one-fluid approximation for a quasi-monopole cold outflow.
Abstract: The effects of radiation drag force on the structure of relativistic electron–positron and electron–proton outflows are considered within the one-fluid approximation for a quasi-monopole cold outflow. It is shown that for a Poynting-dominated case, the drag force does not change the particle energy inside a fast magnetosonic surface. In this region, the action of the drag results in a diminution of the Poynting flux, not the particle flux. Outside the fast magnetosonic surface, for intermediate photon density, the drag force may result in additional acceleration of the plasma. This acceleration is the result of the disturbance of magnetic surfaces under the action of the drag. At even larger distances, particles are not frozen into the magnetic field and the drag force decelerates them efficiently.
In the case of extreme photon densities, the disturbance of magnetic surfaces becomes large and the drag force changes the total energy flux significantly, the particles becoming non-relativistic.
We find that for active galactic nuclei, the photon density is too low to disturb the parameters of an ideal magnetohydrodynamic outflow. The drag action may result in additional acceleration of outgoing plasma only for central engines with very high luminosities. For cosmological gamma-ray bursts, the drag force can strongly affect the process of formation of a Poynting-dominated outflow.
TL;DR: This work investigated correspondence between “gold standard” alignments of 3D protein structures and the sequence alignments produced by the Smith–Waterman algorithm, currently the most sensitive method for pair‐wise alignment of sequences, and suggested an alternative hierarchical algorithm, which explicitly addresses high scoring regions.
Abstract: Alignment of protein sequences is a key step in most computational methods for prediction of protein function and homology-based modeling of three-dimensional (3D)-structure. We investigated correspondence between "gold standard" alignments of 3D protein structures and the sequence alignments produced by the Smith-Waterman algorithm, currently the most sensitive method for pair-wise alignment of sequences. The results of this analysis enabled development of a novel method to align a pair of protein sequences. The comparison of the Smith-Waterman and structure alignments focused on their inner structure and especially on the continuous ungapped alignment segments, "islands" between gaps. Approximately one third of the islands in the gold standard alignments have negative or low positive score, and their recognition is below the sensitivity limit of the Smith-Waterman algorithm. From the alignment accuracy perspective, the time spent by the algorithm while working in these unalignable regions is unnecessary. We considered features of the standard similarity scoring function responsible for this phenomenon and suggested an alternative hierarchical algorithm, which explicitly addresses high scoring regions. This algorithm is considerably faster than the Smith-Waterman algorithm, whereas resulting alignments are in average of the same quality with respect to the gold standard. This finding shows that the decrease of alignment accuracy is not necessarily a price for the computational efficiency.
TL;DR: In this paper, the evolution of an Al preformed plasma produced by a prepulse was observed before and after the arrival of the main pulse by an interferometer using a femtosecond probe pulse.
Abstract: The evolution of an Al preformed plasma produced by a prepulse was observed before and after the arrival of the main pulse by an interferometer using a femtosecond probe pulse. A central density depression due to the ponderomotive force of the main laser pulse in the preformed plasma with a ∼100 μm scale length was clearly visible after the main pulse irradiation at an intensity of ∼5×1016 W/cm2. The temporal profiles of the prepulse, characterized by a cross-correlation in conjunction with a precise density profile measurement by an interferometer, contribute to the better understanding of femtosecond laser-matter interactions.
TL;DR: In this article, the axisymmetric flames are shown to be unstable for any tube width in the case of realistically large thermal expansion, and when thermal expansion is small, they are also unstable for all tube radii of interest.
TL;DR: In this article, the anomalous contribution of Hall resistance to ρH is attributed to the transition from the spin-polaron to coherent regime of electron density fluctuations in the vicinity of Fe centers and to the formation of nanosize ferromagnetic regions.
Abstract: The study of galvanomagnetic, magnetic, and magnetooptical characteristics of iron monosilicide in a wide range of temperatures (1.8–40 K) and magnetic fields (up to 120 kOe) has revealed the origin of the low-temperature sign reversal of the Hall coefficient in FeSi. It is shown that this effect is associated with an increase in the amplitude of the anomalous component of the Hall resistance ρH (the amplitude increases by more than five orders of magnitude with decreasing temperature in the range 1.8–20 K). The emergence of the anomalous contribution to ρH is attributed to the transition from the spin-polaron to coherent regime of electron density fluctuations in the vicinity of Fe centers and to the formation of nanosize ferromagnetic regions, i.e., ferrons (about 10 A in diameter), in the FeSi matrix at T 0, T>Tm) to a negative (Δρ/ρ TC), ferromagnetic (Tm
TL;DR: The conclusion has been made that the drift velocity is a nonrelativistic quantity even at the peak laser intensity of 10(21) W/cm(2), which is much larger than the classical skin depth.
Abstract: The general peculiarities of electron motion in the skin layer at the irradiation of overdense plasma by a superintense linearly polarized laser pulse of femtosecond duration are considered. The quiver electron energy is assumed to be a relativistic quantity. Relativistic electron drift along the propagation of laser radiation produced by a magnetic part of a laser field remains after the end of the laser pulse, unlike the relativistic drift of a free electron in underdense plasma. As a result, the penetration depth is much larger than the classical skin depth. The conclusion has been made that the drift velocity is a nonrelativistic quantity even at the peak laser intensity of 10 2 1 W/cm 2 . The time at which an electron penetrates into field-free matter from the skin layer is much less than the pulse duration.
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TL;DR: It is proved that, for fields n of characteristic 2, such a matrix A can be chosen to be symmetric, and it is shown that a linear MRD code k containing the above-mentioned one-dimensional symmetric code as a subcode has the following property: the corresponding transposed code is also n-linear.
Abstract: As is well known, a finite field \mathbb{K}n e GF(qn) can be described in terms of n × n matrices A over the field \mathbb{K} e GF(q) such that their powers Ai, i e 1, 2, …, qn − 1, correspond to all nonzero elements of the field. It is proved that, for fields \mathbb{K}n of characteristic 2, such a matrix A can be chosen to be symmetric. Several constructions of field-representing symmetric matrices are given. These matrices Ai together with the all-zero matrix can be considered as a \mathbb{K}n-linear matrix code in the rank metric with maximum rank distance d e n and maximum possible cardinality qn. These codes are called symmetric rank codes. In the vector representation, such codes are maximum rank distance (MRD) linear ln, 1, nr codes, which allows one to use known rank-error-correcting algorithms. For symmetric codes, an algorithm of erasure symmetrization is proposed, which considerably reduces the decoding complexity as compared with standard algorithms. It is also shown that a linear ln, k, d e n − k + 1r MRD code \mathcal{V}k containing the above-mentioned one-dimensional symmetric code as a subcode has the following property: the corresponding transposed code is also \mathbb{K}n-linear. Such codes have an extended capability of correcting symmetric errors and erasures.
TL;DR: In this paper, the leptonic constant for the pseudoscalar ground state of the Bc meson was calculated in the framework of a QCD-motivated potential model taking into account the two-loop anomalous dimension for the heavy quark current in nonrelativistic QCD as matched with full QCD.
Abstract: We calculate the leptonic constant for the pseudoscalar ground state of the Bc meson in the framework of a QCD-motivated potential model taking into account the two-loop anomalous dimension for the heavy quark current in nonrelativistic QCD as matched with full QCD.
TL;DR: In this article, a comparison of model calculations with recent helioseismic data ensures more precise determination of solar-plasma composition, showing that the inclusion of additional components to the composition of heavy-element admixtures is a necessary condition for the theoretical equation of state and the results of analysis of solar oscillations to be consistent.
Abstract: The thermodynamic functions of a weakly nonideal plasma are extensively calculated for conditions typical of the depths of stars by using the SAHA-S equation of state. These calculations ensure precise analysis of the effect of the heavy-element content on adiabatic compressibility in the depths of the Sun. Comparison of model calculations with recent helioseismic data ensures more precise determination of solar-plasma composition. This comparison shows that the inclusion of additional components to the composition of heavy-element admixtures is a necessary condition for the theoretical equation of state and the results of analysis of solar oscillations to be consistent.
TL;DR: It is concluded that crystals of bacteriorhodopsin are composed of several macroscopic twinning domains with sizes comparable to the original crystal.
TL;DR: In this paper, the inner and outer multiple ionization of clusters by a superintense ultrashort laser pulse was studied, and the barrier-suppression mechanism governed inner field ionization in this case, while impact ionization can be neglected.
Abstract: Inner and outer multiple ionization of clusters by a superintense ultrashort laser pulse is studied. The barrier-suppression mechanism governs inner field ionization in this case, while impact ionization can be neglected. Outer ionization produces a static Coulomb field inside the ionized cluster. This field increases the charge multiplicity of the atomic ions produced inside the cluster approximately by a factor of 1.5. Various models are suggested for the charge distribution inside the cluster.
TL;DR: In this article, the doubly differential cross section with respect to radiation frequency and angle of radiation is calculated without fitting parameters for the bremsstrahlung in polycrystalline silver.
05 Jan 2004
TL;DR: In this article, a relationship between the receptivity coefficients for sharp and blunt leading edges of a flat plate was established using the concept of effective length, and it was shown that even small bluntness leads to significant decreasing of the perceived receptivity level.
Abstract: Receptivity of supersonic boundary layer to acoustic disturbances interacting with a blunt leading edge of a flat plate is studied using a combined asymptotic and numerical approach. A relationship between the receptivity coefficients for sharp and blunt leading edges is established using the concept of effective length. For the case of receptivity to fast acoustic waves at free-stream Mach number 6, it is shown that even small bluntness leads to significant decreasing of the receptivity level. Nomenclature C = coupling coefficient E = receptivity coefficient F = frequency parameter L = streamwise length scale ef l = effective length b l = wavelength coefficient M = freestream Mach number p = pressure disturbance r = nose radius ** Re /
05 Jan 2004
TL;DR: In this paper, the cosine, optical, and photon-number tomographic symbols of binomial states of the radiation field are studied and explicit relations for all tomograms of these states are obtained.
Abstract: The symplectic, optical, and photon-number tomographic symbols of binomial states of the radiation field are studied. Explicit relations for all tomograms of the binomial states are obtained. Two measures for nonclassical properties of these states are discussed.
TL;DR: In this paper, non-equilibrium electron beam plasma (EBP) was used for surface modification of materials, synthesis of protective coatings, and film deposition at sufficiently high plasma pressures (up to 50 Torr).
Abstract: Non-equilibrium electron beam plasma (EBP) was proved to be promising for surface modification of materials, synthesis of protective coatings, and film deposition at sufficiently high plasma pressures (up to 50 Torr). The optimal EBP parameters were selected to produce active plasma particles in desired concentrations and to heat the surface to the required temperature. Synthesis of nitride, carbide oxide and boride surface layers, carbon and ceramics deposition on polymers at low substrate temperatures, powder treatment in both the dusty EBP and the dust-plasma crystals were studied.