Ignition of boron-containing high-energy materials based on an oxidizer and polymer binder

The use of aluminum borides is a promising direction in the development of modern propellant compositions and aerial vehicles. We present experimental data on the kinetics of oxidation of microscale powders of aluminum, amorphous boron, and the aluminum borides AlB2 and AlB12 in air upon heating at a constant rate of 10°C/min and the results of laser-assisted ignition of high-energy materials that contain these metal powders and are based on ammonium perchlorate, ammonium nitrate, and an inert binder or an energetic combustible binder. We show that the use of the boron-containing powders enables us to lower the onset temperature of oxidation and the temperature of intense oxidation, while increasing their oxidation effectiveness, compared to pure aluminum. The dependences of ignition delay time on the heat flux show that the AlB2 and AlB12 powders are the most effective metal fuel components for solid propellants based on ammonium perchlorate, ammonium nitrate, and an energetic binder: they display the shortest ignition delay time and require the lowest heat input for ignition

Morphology of ceramic particles produced by plasma-chemical synthesis

Thermal and diffusion processes in the droplet weakly concentrated metal salt solution during its heating in the plasma chemical reactor, in order to synthesize metal oxide powders are considered. Numerical study is based on previously proposed physical-mathematical model. The results of numerical calculations are analyzed to assess the possible influence of the operation parameters of the reactor and the characteristics of the initial solution (precursor) on the morphology of the particles formed

Анализ влияния геометрических отклонений рабочих лопаток вентилятора на аэродинамические характеристики ступени

In this article there are the results of the aerodynamic characteristic calculations for the fan blades of the gas turbine engine for the regional aircraft, considering production deviations. The analyzed models of blades with different geometric airfoil deviations, the calculated model of the fan stage, the estimated aerodynamic characteristics are described. Here you can find the example of the calculation results.En este artículo se presentan los resultados de los cálculos de las características aerodinámicas para las aspas del ventilador del motor de turbina de gas para un avión regional, teniendo en cuenta las desviaciones de producción. Asimismo, se describen los modelos analizados de aspas con diferentes desviaciones geométricas de perfil aerodinámico, el modelo calculado de la etapa del ventilador y las características aerodinámicas estimadas. A su vez, los resultados del cálculo se ilustran con un ejemplo.Neste artigo são apresentados os resultados dos cálculos das características aerodinâmicas das pás do ventilador do motor de turbina de gás para um avião regional, tendo em conta os desvios de produção. Além disso, são descritos os modelos analisados de lâminas com diferentes desvios geométricas de perfil aerodinâmico, o modelo calculado da fase do ventilador e as características aerodinâmicas estimadas. Por sua vez, os resultados do cálculo são ilustrados com um exemplo.Представлены результаты расчета аэродинамических характеристик лопаток вентилятора газотурбинного двигателя для регионального самолета с учетом производственных отклонений. Описаны анализируемые модели лопаток с различными геометрическими отклонениями на пере, расчетная модель ступени вентилятора, оцениваемые аэродинамические характеристики, приведен пример результатов расчета

<i>N,N</i>-bis-(dimethylfluorosilylmethyl)amides of <i>N</i>-organosulfonylproline and sarcosine: synthesis, structure, stereodynamic behaviour and <i>in silico</i> studies

(O→Si)-Chelate difluorides R3R2NCH(R1)C(O)N(CH2SiMe2F)2 (9a–c, R1R2 = (CH2)3, R3 = Ms (a), Ts (b); R1 = H, R2 = Me, R3 = Ms (c)), containing one penta- and one tetracoordinate silicon atoms were synthesized by silylmethylation of amides R3R2NCH(R1)C(O)NH2, subsequent hydrolysis of unstable intermediates R3R2NCH(R1)C(O)N(CH2SiMe2Cl)2 (7a–c) into 4-acyl-2,6-disilamorpholines R3R2NCH(R1)C(O)N(CH2SiMe2O)2 (8a–c) and the reaction of the latter compounds with BF3·Et2O. The structures of disilamorpholines 8a,c and difluoride 9a were confirmed by an X-ray diffraction study. According to the IR and NMR data, the O→Si coordination in solutions of these compounds was weaker than that in the solid state due to effective solvation of the Si–F bond. A permutational isomerisation involving an exchange of equatorial Me groups at the pentacoordinate Si atom in complexes 9a–c was detected, and its activational parameters were determined by 1H DNMR. In silico estimation of possible pharmacological effects and acute rat toxicity by PASS Online and GUSAR Online services showed a potential for their further pharmacological study

Complete devil's staircase and crystal--superfluid transitions in a dipolar XXZ spin chain: A trapped ion quantum simulation

Systems with long-range interactions show a variety of intriguing properties: they typically accommodate many meta-stable states, they can give rise to spontaneous formation of supersolids, and they can lead to counterintuitive thermodynamic behavior. However, the increased complexity that comes with long-range interactions strongly hinders theoretical studies. This makes a quantum simulator for long-range models highly desirable. Here, we show that a chain of trapped ions can be used to quantum simulate a one-dimensional model of hard-core bosons with dipolar off-site interaction and tunneling, equivalent to a dipolar XXZ spin-1/2 chain. We explore the rich phase diagram of this model in detail, employing perturbative mean-field theory, exact diagonalization, and quasiexact numerical techniques (density-matrix renormalization group and infinite time evolving block decimation). We find that the complete devil's staircase -- an infinite sequence of crystal states existing at vanishing tunneling -- spreads to a succession of lobes similar to the Mott-lobes found in Bose--Hubbard models. Investigating the melting of these crystal states at increased tunneling, we do not find (contrary to similar two-dimensional models) clear indications of supersolid behavior in the region around the melting transition. However, we find that inside the insulating lobes there are quasi-long range (algebraic) correlations, opposed to models with nearest-neighbor tunneling which show exponential decay of correlations

Genotyping of Capreolus pygargus Fossil DNA from Denisova Cave Reveals Phylogenetic Relationships between Ancient and Modern Populations

BACKGROUND: The extant roe deer (Capreolus Gray, 1821) includes two species: the European roe deer (C. capreolus) and the Siberian roe deer (C. pygargus) that are distinguished by morphological and karyotypical differences. The Siberian roe deer occupies a vast area of Asia and is considerably less studied than the European roe deer. Modern systematics of the Siberian roe deer remain controversial with 4 morphological subspecies. Roe deer fossilized bones are quite abundant in Denisova cave (Altai Mountains, South Siberia), where dozens of both extant and extinct mammalian species from modern Holocene to Middle Pleistocene have been retrieved. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed a 629 bp fragment of the mitochondrial control region from ancient bones of 10 Holocene and four Pleistocene Siberian roe deer from Denisova cave as well as 37 modern specimen belonging to populations from Altai, Tian Shan (Kyrgyzstan), Yakutia, Novosibirsk region and the Russian Far East. Genealogical reconstructions indicated that most Holocene haplotypes were probably ancestral for modern roe deer populations of Western Siberia and Tian Shan. One of the Pleistocene haplotypes was possibly ancestral for modern Yakutian populations, and two extinct Pleistocene haplotypes were close to modern roe deer from Tian Shan and Yakutia. Most modern geographical populations (except for West Siberian Plains) are heterogeneous and there is some tentative evidence for structure. However, we did not find any distinct phylogenetic signal characterizing particular subspecies in either modern or ancient samples. CONCLUSION/SIGNIFICANCE: Analysis of mitochondrial DNA from both ancient and modern samples of Siberian roe deer shed new light on understanding the evolutionary history of roe deer. Our data indicate that during the last 50,000 years multiple replacements of populations of the Siberian roe deer took place in the Altai Mountains correlating with climatic changes. The Siberian roe deer represent a complex and heterogeneous species with high migration rates and without evident subspecies structure. Low genetic diversity of the West Siberian Plain population indicates a recent bottleneck or founder effect

Emergency Shut-Down Valve for Gas Pipelines by Alexander Vorozhtsov, V. Arkhipov, and I. Plekhanov; Strategic Insights, v. 7 issue 1 (February 2008)

This article appeared in Strategic Insights, v.7 issue 1 (February 2008)Approved for public release; distribution is unlimited

Orbitron-type vacuum gauge with nanocarbon field cathode

A novel electron–optical scheme of ionization-type vacuum gauge is proposed that allows the use of field-emission nanocarbon cathodes. The developed gauge satisfies the requirements imposed by possible utilization in on-board satellite equipment: low mass, size and energy consumption, low turn-on time, etc. High efficiency and sensitivity of the sensor are achieved by the use of an electrostatic trap for accumulation of electrons ionizing the gas molecules. Magnetic field was not used for mass economy reason and to avoid possible influence onto other on-board equipment. The main problem solved in the work originated from the intrinsic contradiction between the aims of achieving long-term confinement of electrons in the trap and focusing of the applied electric field at the cathode, the latter being necessary to utilize the phenomenon of field-induced emission. Experimental tests were performed with two prototype devices realizing different versions the electron-scheme design, viability of both developed schemes has been confirmed

Analyzer of high-load electron beams with resolution in two energy components, space and time

The new apparatus is developed for experimental determination of electron energy and spatial distributions in dense medium-energy long-pulsed magnetically confined beams – typically, 10 A/cm2, 60 keV, 100 µs, 0.1 T. To provide most detailed and unambiguous information, direct electrostatic cut-off method is used for electron energy analysis. In combination with variation of the magnetic field in the analysis area, this method allows to determine both (axial and transverse) components of electron energy. Test experiments confirmed ∼1% energy resolution being predicted from calculations, accounting for electrode shapes, space-charge effects and non-adiabatic energy transfer effects in varied magnetic field. Space and time resolution of the apparatus are determined by the input aperture size (∼1 mm) and cut-off electric field pulse-length (∼5–10 µs) respectively