Effect of perturbed flow on the transition from the supersonic laminar boundary layer to the turbulent

Results of experimental studies on the effect of various factors on the transition of a supersonic boundary layer are discussed. It is shown that in supersonic wind tunnels, a significant effect on the transition of the boundary layer on a model is exerted by the scale of acoustic perturbations, which is proportional to the boundary layer displacement thickness of the working section. Experimental data obtained over a wide range of variation of flow parameters in aerodynamically similar test installations with different dimensions of the working section are generalized by means of a correlation parameter based on the displacement thickness

Productivity of corn hybrids in relation to the seeding rate

ArticlePotential yield of corn hybrids with a different FAO number is limited by not only rainfall amount, average soil and air temperature throughout vegetation period, but also directly depends on plant density. The study and practical application of special agricultural techniques allows us to limit and mitigate the negative impact of these factors on the productivity of maize, depending on the indicators under study and the soil and climatic resources of the cultivation zone. Therefore, the study of the influence of the seeding rate on the growth and development of corn plants remains relevant. The results presented make it possible to choose optimal seeding rates for corn hybrids of early and middle groups of ripeness (FAO 180-280). Overcrowding from 61,000 to 93,000 seeds ha-1 leads to increase in interstage period 'sprouting–wax ripeness' of Rodnik 179SV hybrid for 4 days, of MAS 12R and AMELIOR hybrids–for 2 days, and of MAS 30K hybrid – for 3 days. Hybrids Rodnik 179SV and AMELIOR reached maximum height – 217 cm and 214 cm respectively – at seeding rate of 73,000 seeds ha-1 , while hybrids MAS 12R and MAS 30K grew up to their 213 cm and 223 cm respectively at seeding rate of 77,000 seeds ha-1 . Decrease in seeding rate to less than 73,000 seeds ha-1 and, contrary to it, overcrowding of seeds of more than 77,000 seeds ha-1 leads to decrease in corn hybrid plant height. Agronomically, the most efficient for maximizing early ripe Rodnik 179SV and MAS 12R hybrids yields (6.39 and 6.73 t ha-1 ) and middle-early ripe AMELIOR hybrid yield (6.81 t ha-1 ) was the seeding rate of 73,000 seeds ha-1 , while the highest yield of middle MAS 30K hybrid (7.21 t ha-1 ) was at the seeding rate of 77,000 seeds ha-1

Canted antiferromagnetic phase of the ν=0\nu=0 quantum Hall state in bilayer graphene

Motivated to understand the nature of the strongly insulating $\nu=0$ quantum Hall state in bilayer graphene, we develop the theory of the state in the framework of quantum Hall ferromagnetism. The generic phase diagram, obtained in the presence of the isospin anisotropy, perpendicular electric field, and Zeeman effect, consists of the spin-polarized ferromagnetic (F), canted antiferromagnetic (CAF), and partially (PLP) and fully (FLP) layer-polarized phases. We address the edge transport properties of the phases. Comparing our findings with the recent data on suspended dual-gated devices, we conclude that the insulating $\nu=0$ state realized in bilayer graphene at lower electric field is the CAF phase. We also predict a continuous and a sharp insulator-metal phase transition upon tilting the magnetic field from the insulating CAF and FLP phases, respectively, to the F phase with metallic edge conductance $2e^2/h$, which could be within the reach of available fields and could allow one to identify and distinguish the phases experimentally.Comment: 5 pages, 3 figs; v2: published versio

Enhancement of Superconductivity in Disordered Films by Parallel Magnetic Field

We show that the superconducting transition temperature T_c(H) of a very thin highly disordered film with strong spin-orbital scattering can be increased by parallel magnetic field H. This effect is due to polarization of magnetic impurity spins which reduces the full exchange scattering rate of electrons; the largest effect is predicted for spin-1/2 impurities. Moreover, for some range of magnetic impurity concentrations the phenomenon of {\it superconductivity induced by magnetic field} is predicted: superconducting transition temperature T_c(H) is found to be nonzero in the range of magnetic fields $0 < H^* <= H <= H_c$.Comment: 4 pages, 2 figure

Геохімічна оцінка ефективності застосування прошарку лесоподібного суглинку для екранування фітотоксичних шахтних порід у Західному Донбасі

Main environmental threats of the excavated rocks and gobs in theWestern Donbassare pollution of soils and subterranean waters by toxic salts and heavy metals. Use of the three-layered models with a stratum of protective shield of the loess-like loamy soil for the restoration considerably decreases this negative impact.Основна загроза для довкілля від шахтних порід, що видобуваються разом із кам’яним вугіллям у Західному Донбасі, пов’язана із забрудненням ґрунтів і ґрунтових вод токсичними солями та важкими металами. Суттєве зниження цього негативного впливу, у разі подальшого сільськогосподарського використання порушених земель, можливе із застосуванням тришарових моделей рекультивації з прошарком захисного екрана лесоподібного суглинку.Основна загроза для довкілля від шахтних порід, що видобуваються разом із кам’яним вугіллям у Західному Донбасі, пов’язана із забрудненням ґрунтів і ґрунтових вод токсичними солями та важкими металами. Суттєве зниження цього негативного впливу, у разі подальшого сільськогосподарського використання порушених земель, можливе із застосуванням тришарових моделей рекультивації з прошарком захисного екрана лесоподібного суглинку

Subexponential estimations in Shirshov's height theorem (in English)

In 1993 E. I. Zelmanov asked the following question in Dniester Notebook: "Suppose that F_{2, m} is a 2-generated associative ring with the identity x^m=0. Is it true, that the nilpotency degree of F_{2, m} has exponential growth?" We show that the nilpotency degree of l-generated associative algebra with the identity x^d=0 is smaller than Psi(d,d,l), where Psi(n,d,l)=2^{18} l (nd)^{3 log_3 (nd)+13}d^2. We give the definitive answer to E. I. Zelmanov by this result. It is the consequence of one fact, which is based on combinatorics of words. Let l, n and d>n be positive integers. Then all the words over alphabet of cardinality l which length is greater than Psi(n,d,l) are either n-divided or contain d-th power of subword, where a word W is n-divided, if it can be represented in the following form W=W_0 W_1...W_n such that W_1 >' W_2>'...>'W_n. The symbol >' means lexicographical order here. A. I. Shirshov proved that the set of non n-divided words over alphabet of cardinality l has bounded height h over the set Y consisting of all the words of degree <n. Original Shirshov's estimation was just recursive, in 1982 double exponent was obtained by A.G.Kolotov and in 1993 A.Ya.Belov obtained exponential estimation. We show, that h<Phi(n,l), where Phi(n,l) = 2^{87} n^{12 log_3 n + 48} l. Our proof uses Latyshev idea of Dilworth theorem application.Comment: 21 pages, Russian version of the article is located at the link arXiv:1101.4909; Sbornik: Mathematics, 203:4 (2012), 534 -- 55

Anomaly crust fields from MAGSAT satellite measurements:their processing and interpretation

The space distribution of the magnetic anomaly field for the Pacific Ocean is obtained from data of the satellite MAGSAT. A number of long-wavelength magnetic anomalies of the region are identified. A spectrum analysis of a number of profiles of the anomaly field is performed disclosing typical scales of such anomalies. The wave transform of the anomaly magnetic profiles reveals and explicitly exposes the structure of the considered profile. A schematic complex cross-section is constructed, which demonstrates that the satellite data may be used in the study of the magnetic anomaly