On the Stability of Rod with Variable Cross-section

AbstractThere is a solution of the problem of the stability of a compressed rod with a variable cross-section. A rectangular cross-section with a variable width is selected as the section. The result is that the problem leads to a differential equation of the fourth order with variable coefficients. From the solution of this equation, a critical force for several particular cases. These cases reflect some different conditions fixing rod and function changes of the width of the cross-section

Calculation of radially inhomogeneous ring loaded with normal and tangential loads

The aim of the study is to solve the problem of the stress-strain state of a thin ring under radial and ring loads, factoring in the radial inhomogeneity of the ring. Also, the task is to compare the two calculation methods to the example of solving the problem of uneven load distribution along the outer surface of the ring with one-dimensional inhomogenuity. Analytical or numerical-analytical solutions are used in the two-dimensional plane problem of the theory of elasticity in polar coordinates for an inhomogeneous body. Most of these problems consider centrally symmetric circular bodies. As a rule, this is possible when all unknown functions depend on the radius. These tasks correspond with the majority of ring and cylindrical structures. Pipes are suitable for creating pipeline systems and civil engineering, they are used for gas pipelines, in heating networks and water supply systems. The key feature of the work lies in the consideration of uneven radial and ring loads distribution along the outer surface of the ring. Comparison of the calculation results obtained by two methods makes it possible to determine the stressed and deformed states with sufficient accuracy, an indicator of which is the obtaining of the ring stresses

Pollen and Isotope Investigations of an Ice Core from Vavilov Ice Cap, October Revolution Island, Severnaya Zemlya Archipelago, Russia

The Vavilov Ice Cap (79°27'N, 95° 21'E) was cored during February and March of 1988. The corer passed through 457.18 m of glacier ice, 2.15 m of moraine-containing ice, and 2.28 m of underlying rocks. Structural-stratigraphical and isotope analysis show the glacier ice is of Holocene in age; the ice layer covered by frozen deposits is Pleistocene glacier ice; and the ground (ice wedge?) ice from underlying sediments was formed during the Last Interglacial. Palynological studies of this core, carried out for the first time in the Russian Arctic demonstrate that the pollen spectra have a unique pattern. It reduces the possibility of correlation between the Vavilov Ice Cape spectra and pollen spectra from other surficial deposits, because the ice retains pollen and spores brought from enormous distances. Only the upper 65 m of the core is easily dated, to the last millennium, by the presence of cereals, Plantago lanceolata, Centaurea cyanus, Cannabis pollen. That is in good agreement with the model of age distribution based upon depth. The presence of considerable amounts of Tilia cordifolia pollen, a West-European species in the upper layers suggests that summer air masses have been dominantly from the southwest during the last 500 years. The pollen data do not contradict the conclusion the Vavilov ice core is composed of a section of Holocene ice, moraine-containing ice representing the Pleistocene episode, and a ground ice formed during an earlier warm period (Last Interglacial?).Une carotte de glace prélevée en 1988 au sein de la calotte glaciaire de Vavilov (79°27'N, 95°21'E) a fait l'objet d'analyses isotopiques et palynologiques. Le sondage comprend 457,18 m de glace « pure », suivis de 2,15 m de glace chargée de sédiments et 2,28 m de roches gelés du socle. Les résultats des analyses structurales, stratigraphiques et isotopiques sont les suivants : la glace pure datée de l'Holocène, les 2,15 de la couche chargée de sédiments datent du Pléistocène, tandis que la glace présente dans les fentes du socle s'est formée au cours du dernier interglaciaire. Les spectres polliniques de cette carotte sont caractérisés par des grains de pollen d'origine lointaine préservés dans la glace. Cette constatation réduit grandement les possibilités de corrélation avec les données sédimentaires de la région, qui reflètent la composition de la végétation locale. Un âge inférieur à 1000 ans peut être attribué aux 65 m supérieurs de la carotte en raison de la présence de pollen de céréales, de Plantago lanceolata, Centaurea cyanus et de Cannabis. Cette interprétation concorde avec le modèle du taux d'accumulation de la glace. Dans la partie supérieure de la carotte, la présence en quantité considérable de Tilia cordifolia, une espèce de tilleul d'Europe de l'Ouest, laisse supposer que les masses d'air en provenance du sud-ouest ont prédominé au cours des étés des 500 dernières années. En conclusion, les données palynologiques ne contredisent pas les résultats antérieurs selon lesquels la carotte glaciaire étudiée couvre une partie de l'Holocène, que la glace contenant la moraine représente l'épisode du Pléistocène et que la glace du socle se soit formée pendant une période chaude (le dernier interglaciaire?)

Properties of quantizer and dequantizer operators for qudit states and parametric down-conversion

We review the method of quantizers and dequantizers to construct an invertible map of the density operators onto functions including probability distributions and discuss in detail examples of qubit and qutrit states. The biphoton states existing in the process of parametric down-conversion are studied in the probability representation of quantum mechanics

Radiation of high-power ultrawideband pulses with elliptical polarization by a conical helical antenna

A high-power source of ultrawideband radiation with elliptical polarization was developed on the basis of exciting a conical helical antenna by a bipolar voltage pulse with a length of 1 ns. The antenna parameters were preliminarily estimated using analytical formulas and then optimized via numerical simulation. The results of low-voltage test measurements were compared with the data that were obtained using a program that was developed on the basis of the finite-difference method in the time domain. In high-voltage measurements, the energy efficiency of the radiator was 0.85 and the coefficient of the hodograph ellipticity measured along the antenna axis was 0.9. The effective radiation potential of the source at an amplitude of bipolar voltage pulses of 190 kV was 270 kV, while the efficiency with respect to the peak field strength was 1.35. The high-power source of ultrawideband radiation operated at a pulse repetition frequency of 100 Hz

In celebration of the 60th birthday of Professor Alemdar Hasanoğlu (Hasanov)

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Magnetic field influence on the proximity effect in semiconductor - superconductor hybrid structures and their thermal conductance

We show that a magnetic field can influnce the proximity effect in NS junctions via diamagnetic screening current flowing in the superconductor. Using ballistic quasi-one-dimensional (Q1D) electron channels as an example, we show that the supercurrent flow shifts the proximity-induced minigap in the excitation spectrum of a Q1D system from the Fermi level to higher quasiparticle energies. Thermal conductance of a Q1D channel (normalized by that of a normal Q1D ballistic system) is predicted to manifest such a spectral feature as a nonmonotonic behavior at temperatures corresponding to the energy of excitation into the gapful part of the spectrum.Comment: 5 pages, 3 figures, revised version with a new titl

Inverse spin-s portrait and representation of qudit states by single probability vectors

Using the tomographic probability representation of qudit states and the inverse spin-portrait method, we suggest a bijective map of the qudit density operator onto a single probability distribution. Within the framework of the approach proposed, any quantum spin-j state is associated with the (2j+1)(4j+1)-dimensional probability vector whose components are labeled by spin projections and points on the sphere. Such a vector has a clear physical meaning and can be relatively easily measured. Quantum states form a convex subset of the 2j(4j+3) simplex, with the boundary being illustrated for qubits (j=1/2) and qutrits (j=1). A relation to the (2j+1)^2- and (2j+1)(2j+2)-dimensional probability vectors is established in terms of spin-s portraits. We also address an auxiliary problem of the optimum reconstruction of qudit states, where the optimality implies a minimum relative error of the density matrix due to the errors in measured probabilities.Comment: 23 pages, 4 figures, PDF LaTeX, submitted to the Journal of Russian Laser Researc