Showing papers by "Tomsk Polytechnic University published in 2006"
TL;DR: In this article, the results of DTA-TG investigation and chemical analysis of electro-exploded aluminum nanopowders, passivated and/or coated with the non-inert reagents: nitrocellulose (NC), oleic acid (C17H33COOH), and stearic acid(C 17H35COOCH), which were suspended in kerosene and ethanol, amorphous boron, nickel, fluoropolymer, ethanol and air (for comparison), are discussed.
Abstract: Results of DTA-TG investigation and chemical analysis of electro-exploded aluminum nanopowders, passivated and/or coated with the non-inert reagents: nitrocellulose (NC), oleic acid (C17H33COOH) and stearic acid (C17H35COOH), which were suspended in kerosene and ethanol, amorphous boron, nickel, fluoropolymer, ethanol and air (for comparison), are discussed. Surface protection of aluminum nanopowders by coatings of different origin results in significant advantages in the energetic properties of the powders. Aluminum nanopowders with a protecting surface show increased stability to oxidation in nitrogen, air and in water during storage period. On the basis of the experimental results, a diagram of the formation and stabilization of the coatings is proposed. The kinetics of the interaction of aluminum nanopowders with nitrogen, air and water is discussed. Recommendations concerning the efficiency of non-inert reagent passivation are proposed on the basis of comprehensive analysis of the experimental data.
88 citations
TL;DR: In this article, the surface morphology, chemical composition, microstructure, nanohardness, and tribological properties of a film (Cu)-substrate (stainless steel 316) system subjected to pulsed melting with a low-energy (20-30 keV), high-current electron beam (2.8-8.4 J/cm 2 ) have been investigated.
Abstract: The surface morphology, chemical composition, microstructure, nanohardness, and tribological properties of a film (Cu)–substrate (stainless steel 316) system subjected to pulsed melting with a low-energy (20–30 keV), high-current electron beam (2–3 μs, 2.8–8.4 J/cm 2 ) have been investigated. The film was deposited by sputtering a Cu target in the Ar plasma of a microwave discharge. To prevent the local delamination of the film due to the cratering, the substrates were repeatedly pre-irradiated with 8–10 J/cm 2 . Single pulsed melting of this system resulted in the formation of a diffusion layer of thickness 120–170 nm near the interface, irrespective of the energy density. The layer has the subgrain structure consisting of the γ-Fe-solid solution and submicrometer or nanocrystalline Cu particles. The nanohardness and the wear resistance of the surface layer of thickness 0.5–1 μm, including the molten film and the diffusion layer, non-monotonically vary with energy density, reaching a maximum in the range of 4.3–6.3 J/cm 2 . As the pulse number is increased to five in the same range of energy density, the film dissolves in the substrate, and a ∼2-μm-thick surface layer is formed which contains ∼20 at.% Cu. Under these conditions, the segregation of Cu during resolidification leads to the formation of two-phase nanocrystalline layers separating γ-phase grains.
85 citations
TL;DR: In this paper, a comprehensive characterisation of electro-exploded aluminum nanopowders, passivated with the non-inert reagents: oleic acid (C17H33COOH) and stearic acid(C 17H35COCOH), which were suspended in kerosene and ethanol, was discussed.
80 citations
TL;DR: Both copper(II) complexes exhibited superoxide dismutase (SOD) like activity toward extracellular and intracellular reactive oxygen species produced by activated human neutrophils in whole blood and represent useful SOD mimetics with a broad range of antioxidant activity toward a variety of reactive oxidants.
Abstract: Two bis(1-pyrazolyl)alkane ligands, bis(3,5-dimethyl-1-pyrazolyl)methane and bis(4-iodo-3,5-dimethyl-1-pyrazolyl)methane, and their copper(II) complexes, bis(3,5-dimethyl-1-pyrazolyl)methanedinitratocopper(II) [CuL1(NO3)2] and bis(4-iodo-3,5-dimethyl-1-pyrazolyl)methanedinitratocopper(II) [CuL2(NO3)2]·2H2O, were prepared. Physiochemical properties of the copper(II) complexes were studied by spectroscopic (UV–vis, IR, EPR) techniques and cyclic voltammetry. Spectroscopic analysis revealed a 1:1 stoichiometry of ligand:copper(II) ion and a bindentate coordination mode for the nitrate ions in both of the complexes. According to experimental and theoretical ab initio data, the copper(II) ion is located in an octahedral hexacoordinated environment. Both complexes were able to catalyze the dismutation of superoxide anion (\( {\text{O}}^{{\bullet - }}_{{\text{2}}} \)) (pH 7.5) and decomposition of H2O2 (pH 7.5) and peroxynitrite (pH 10.9). In addition, both complexes exhibited superoxide dismutase (SOD) like activity toward extracellular and intracellular reactive oxygen species produced by activated human neutrophils in whole blood. Thus, these complexes represent useful SOD mimetics with a broad range of antioxidant activity toward a variety of reactive oxidants.
66 citations
TL;DR: In this paper, a general gauge invariant Lagrangian construction was proposed for higher spin fermionic fields in arbitrary dimensions. But the authors only considered the case of massive spin 3/2 fields.
65 citations
TL;DR: In this paper, a universal method of relating the Calogero model to a set of decoupled particles on the real line is proposed, which can be uniformly applied to both the conformal and nonconformal versions as well as to supersymmetric extensions.
62 citations
TL;DR: A multiple focus group method is carried out to rank factors that affect the success of IT-supported ITT and a branch and bound method is applied to derive a consensus ranking of these factors, which sheds light on factors similar to those of DOI theory.
50 citations
TL;DR: In this paper, the electrical and optical parameters of pulsed dielectric barrier discharge (PDBD) were investigated in humid air containing water droplets as a means of water oxidative treatment with short-living species generated in the discharge zone.
Abstract: Experimental research into the electrical and optical parameters of pulsed dielectric barrier discharge (PDBD) was undertaken. PDBD was applied to humid air containing water droplets as a means of water oxidative treatment with short-living species generated in the discharge zone. In spectral analysis of PDBD, only small concentrations of nitric oxides were detected at the resulting electric field strength and electron mean energy sufficient for generation of OH-radicals. The water droplets served as electric field strength concentrators: PDBD was ignited close to the water droplets' surface.
48 citations
TL;DR: In this paper, processes of nonisothermal oxidation, nitridation, and ageing of aluminum powders with different particle sizes (nano-sized powder, ASD-1 powder, and PAP-2 powder) are considered.
Abstract: Processes of nonisothermal oxidation, nitridation, and ageing of aluminum powders with different particle sizes (nano-sized powder, ASD-1 powder, and PAP-2 powder) are considered. Application of non-oxide coatings onto particles of aluminum nanopowders reduces their thermal stability. Owing to scale-shaped particles, the PAP-2 powder after long-time storage preserves high activity of oxidation and nitridation, which is commensurable with that of the aluminum nanopowder. The activity of the coarse ASD-1 powder consisting of spherical particles in terms of oxidation and nitridation is low and only slightly changes during ageing.
36 citations
TL;DR: In this article, the authors investigated the relationship between anomalous gold concentrations and organic matter in low-ash coals and peat and found that about 95% of gold is combined with organic matter.
32 citations
TL;DR: The influence of copper modifying additive on state of gold in NaY and NH 4 -mordenite has been investigated in this article, where the presence of copper in Au/Cu/NM permits to stabilize fine gold particles (∼8nm), while for Au/cu/NaY large particles with unusual complex structure and size up to 80nm were registered.
TL;DR: In this article, a 3 × 3 matrix of samples has been ion implanted with nitrogen at low-to-high doses and low to high current densities (dose rates) and all samples show surface exfoliation which results in a loss of the implanted nitrogen and a consequent loss of wear-resistant properties.
Abstract: A 3 × 3 matrix of samples has been ion implanted with nitrogen at low-to-high doses and low-to-high current densities (dose rates). All samples show surface exfoliation which results in a loss of the implanted nitrogen and a consequent loss of the wear-resistant properties—a condition of over-implantation reminiscent of that observed with metal ion implantation. There is an uptake of post-implantation oxygen which is believed to form an amorphous TiO2 component in the surface leading to the well-established low frictional properties. This uptake decreases as the dose rate is increased and would lead to a loss of wear resistant properties. The work confirms that a dose of 3 × 1017 ions cm− 2 is optimal provided that the dose rate does not exceed the present industrial standard.
TL;DR: In this article, the voltammetric curves of a set of individual current peaks given by particulate reduction of surface oxides on impingements of particles from their suspension upon the electrode correspond to electroactivity of dissolved products of chemical reaction between particles and the medium.
Abstract: Ultrafine powder samples of Cu, Fe, Ni, Mo and W were examined voltammetrically in aqueous suspensions with hanging mercury drop electrode. According to chemical interaction of the metallic powder particles with the dispersing medium the voltammetric curves either consist of a set of individual current peaks given by particulate reduction of surface oxides on impingements of particles from their suspension upon the electrode, or correspond to electroactivity of dissolved products of chemical reaction between particles and the medium.
TL;DR: In this article, a double-probe spreading resistance measurement technique combined with a layer-by-layer analysis was used to investigate the temperature dependences of electroconductivity of polycrystalline lithium pentaferrite (LPF), which was produced via a ceramic-production technological process.
Abstract: Using a double-probe spreading resistance measurement technique combined with a layer-by-layer analysis, temperature dependences of electroconductivity of polycrystalline lithium pentaferrite (LPF), which is produced via a ceramic-production technological process, are investigated. It is shown that the electroconductivity activation energy of LPF is controlled by the height of grain-boundary potential barrier due to different degrees of grain boundary and grain bulk oxidation. A relationship is established between the value of the electroconductivity activation energy of LPF and the processes of its oxygen exchange with the surrounding medium during thermal annealing.
TL;DR: The general approach to the detailed characterizing of peak properties based on the use of characteristic points on a peak contour located at the certain levels is proposed.
TL;DR: In this article, a model of the intergranular layer in the ceramic is considered, which explains the temperature dependence of the phonon diffusion coefficient, makes it possible to determine the inter granular layer parameters (density, velocity of sound, and thickness), and gives an idea about its structure.
Abstract: Phonon transfer in yttrium-oxide (Y2O3) stabilized ZrO2 ceramics is studied experimentally in the range of helium temperatures (1.7–3.8 K). A model of the structure of the intergranular layer in the ceramic is considered, which explains the temperature dependence of the phonon diffusion coefficient, makes it possible to determine the intergranular layer parameters (density, velocity of sound, and thickness), and gives an idea about its structure. Scattering of injected phonons from resonance vibrations of nanoceramic grains is discussed.
TL;DR: In this article, a possibility of existing spheres filled with a uniform constant scalar field in the universe is shown, which can act as "dark matter" and can be responsible for a decreasing behavior of the " rotational" curved galaxies observed.
Abstract: A possibility of existing spheres filled with a uniform constant scalar field in the Universe is shown. These spheres can act as “dark matter” and can be responsible for a decreasing behavior of the “ rotational” curved galaxies observed.
01 Nov 2006-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the authors considered the transition radiation from a relativistic charge crossing a finite radius paraboloid target with taking into account the pre-wave zone effect and showed that in this case the radiation cone narrowing occurs in contrast with that from the flat target if the detector is situated at the distance, which is smaller than the focus distance (the focusing effect) from the target.
Abstract: In the article the transition radiation from a relativistic charge crossing a finite radius paraboloid target with taking into account the pre-wave zone effect is considered. It is shown that in this case the radiation cone narrowing occurs in contrast with the transition radiation from the flat target if the detector is situated at the distance, which is smaller than the focus distance (the focusing effect) from the target. At the charged particle passage through the central hole in a paraboloid target the diffraction radiation focusing (DR) occurs too. The focusing of coherent DR for the non-invasive measuring of the electron bunch length is proposed.
TL;DR: In this paper, the authors studied the quantum properties of two theories with a nonanticommutative (or nilpotent) chiral singlet deformation of N = ( 1, 1 ) supersymmetry.
TL;DR: The transition from a planned centralist economy to a market economy over the last decade of the 20th century has presented Russian universities with many profound challenges and these challenges require universities to review and consider their organisational culture and deserve careful study.
Abstract: The transition from a planned centralist economy to a market economy over the last decade of the 20th century has presented Russian universities with many profound challenges. These challenges require universities to review and consider their organisational culture and deserve careful study. This paper describes the changes that have taken place at Tomsk Polytechnic University ‐ one of oldest, largest and leading Russian universities.
TL;DR: Intramolecular Diels–Alder reaction of these vinylsulfonamides with thermal or high pressure activation provides efficient access to a range of γ- and δ-sultams following a 2–3 d long synthetic procedure.
Abstract: Vinylsulfonamides with a furan, carbocyclic, semicyclic or acyclic 1,3-diene moiety are synthetized via a domino elimination–amidation reaction of 2-chloroethanesulfonyl chloride. Intramolecular Diels–Alder reaction of these vinylsulfonamides with thermal (toluene, 110 °C) or high pressure (dichloromethane, 13 kbar) activation provides efficient access to a range of γ- and δ-sultams following a 2–3 d long synthetic procedure. Enantiopure sultams are readily obtained from N-1-phenylethyl substituted vinylsulfonamides.
TL;DR: In this article, the autoclave breakdown of zircon with ammonium fluorides was studied and the results showed that ammonium fluoride reacts slowly with ZrSiO4 and ammonium tetrafluoride.
Abstract: Autoclave breakdown of zircon with ammonium fluorides was studied. DOI: 10.1134/S1070427206110036 Zircon is one of the main mineral sources of zirconium materials, but the technology of its breakdown and processing is still labor-consuming, and much efforts are made to improve it. The classical industrial methods of breaking down zirconium concentrates are sintering with fluosilicates and chlorination. Numerous studies summarized in [1] were devoted to zircon fluorination; however, it did not gain industrial application. The fluoride technology allows the scheme of the zirconium product processing to be reduced considerably, but high cost and corrosive behavior of HF and F2, and also SiF4 liberation restrain industrial application of these reagents. In this study we examined the autoclave breakdown of zircon with ammonium fluorides. Unlike fluorine and hydrogen fluoride, ammonium fluorides are very convenient to use, as these are solid crystalline substances under normal conditions. Ammonium fluorides can be obtained from metal fluorides by the action of ammonia water, which is the basis for conversion and recycling of ammonium fluorides. Ammonium fluoride is known to react slowly with zircon [2, 3]. At temperatures below 240 C, the reaction rate is negligible and the degree of breakdown is unsatisfactory for the industrial use, whereas at higher temperatures ammonium fluoride evaporates with decomposition. Here we report new data on the zircon breakdown with ammonium fluoride and hydrofluoride. The essence of the method consists in the reaction of zircon with ammonium fluoride or hydrofluoride under isochoric conditions (in an autoclave), after which the reaction products are separated by sublimation to give zirconium tetrafluoride and dioxide. The advantage of ammonium fluorides over other fluorinating agents consists in their convenient physicochemical properties allowing their regeneration and recycling. The experiments were carried out with zircon samples from Tugan deposit of Tomsk oblast. The reactions of zircon with ammonium fluoride and hydrofluoride were studied under isochoric conditions in a 100 cm3 stainless steel autoclave. A weighed portion of zircon with a grain size of 0.074 mm was placed in the autoclave together with a weighed portion of ammonium fluoride taken in a 20% excess in relation to the stoichiometric amount calculated for the reaction ZrSiO4 + 13NH4F = (NH4)3ZrF7 + (NH4)2SiF6 + 8NH3 + 4H2O. The autoclave was heated to 150, 200, 250, 300, 350, and 400 C and kept at these temperatures for 0.5, 1, 2, and 4 h. After opening the autoclave, its content was transferred into a crucible and calcined for 30 min at 400 C to remove by sublimation unchanged NH4F and formed (NH4)2SiF6. The residue in the crucible was a mixture of unchanged ZrSiO4 and NH4ZrF5, to which 5 ml of concentrated sulfuric acid was added, and the mixture was kept until H2SO4 vapor disappeared. Zirconium in the form of ZrOSO4 solution was leached with water from the formed cake, converted to zirconium dioxide, and weighed to determine the degree of conversion. The same procedure was used to study the reaction of ammonium hydrofluoride with zircon 2ZrSiO4 + 13NH4F HF = 2(NH4)3ZrF7 + 2(NH4)2SiF6 + 3NH3 + 8H2O.
01 Nov 2006-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the Smith-Purcell radiation (SPR) characteristics of flat and volume gratings were compared with the 6-MeV microtron in the millimeter wavelength region under coherent conditions.
Abstract: Gratings with different profiles such as lamellar, triangular, sinusoidal (so-called “volume” gratings) and “flat” gratings consisting of thin conductive strips separated by vacuum or dielectric gaps, have been used for investigation of Smith–Purcell radiation (SPR) in a number of experimental and theoretical reports. Some theoretical models predict that the flat grating is more preferable in respect to the radiation intensity. The azimutal dependence of SPR yield from volume and flat gratings is drastically different. However, till now the direct comparison of SPR characteristics for these profiles for the same experimental conditions is absent. We present some experimental results for such comparison obtained with the 6-MeV microtron in millimeter wavelength region under coherent conditions. Radiation angular distribution from gratings of different profiles has been studied in different spectral regions. The flat thin periodical target was demonstrated to have a superior radiation capacity. An additional result of this experiments is the observation of anomalous large long wave radiation intensity at small observation angles, which is not predicted by existing SPR theory. Calculations of SPR characteristics from volume and flat gratings using traditional models, presented in this article are in agreement with experiment only for a large polar angle.
TL;DR: In this paper, a countable set of asymptotic space-localized solutions is constructed by the complex germ method in the adiabatic approximation for the nonstationary Gross-Pitaevskii equation with nonlocal nonlinearity and a quadratic potential.
Abstract: A countable set of asymptotic space-localized solutions is constructed by the complex germ method in the adiabatic approximation for the nonstationary Gross–Pitaevskii equation with nonlocal nonlinearity and a quadratic potential. The asymptotic parameter is 1/T, where T 1 is the adiabatic evolution time. A generalization of the Berry phase of the linear Schrodinger equation is formulated for the Gross–Pitaevskii equation. For the solutions constructed, the Berry phases are found in explicit form.
TL;DR: In this article, the emission yield of X-ray diffraction radiation from ultra-relativistic electrons moving near an absorbing target is considered and shown to increase significantly in conditions of Cherenkov effect.
01 Sep 2006
TL;DR: In this paper, a new base structure of the voltage-controlled phase invariant attenuator is described, which is based on T-attenuator with phase decoupling circuits.
Abstract: A new base structure of the voltage-controlled phase invariant attenuator is described. This structure is based on T-attenuator with phase decoupling circuits. Design factors for decreasing the phase shift are discussed. A computer-aided design technique for minimizing phase shift in attenuator is presented. Measured attenuation of one section up to 15 dB is shown to be independent of frequency band up to 3 GHz. The adjusting parameters for one-stage attenuator were founded. Novelty of this paper consists in application of theorem of the minimum phase shift for the linear attenuator design.
TL;DR: Investigation results of charge state of monocomponent plasma ofTi, Zr, W, and N, as well as that of multicomponent metal plasma of Ti/Zr using plasma-immersion time-of-flight spectrometer are presented in the paper.
Abstract: Investigation results of charge state of monocomponent plasma of Ti, Zr, W, and N, as well as that of multicomponent metal plasma of Ti/Zr (50/50 at.%) using plasma-immersion time-of-flight spectrometer are presented in the paper. The case of pressure impact in the working chamber on the ion charge state of combined metal (Ti) and gas-discharge (N) plasma is considered.
TL;DR: In this paper, the effect of an external ion beam on the plasma and target of a dc magnetron sputtering system in the course of reactive deposition of films is investigated, and it is shown that the ion assistance expands the operating range of the magnetron diode, increases the deposition rate, and substantially shortens the target training time.
Abstract: The effect of an external ion beam on the plasma and target of a dc magnetron sputtering system in the course of reactive deposition of films is investigated. A combined experimental setup consisting of a magnetron diode and a hall-current ion source is constructed. The influence of a fast ion beam on the discharge current formation, the target emission characteristics, and the target etching rate is considered. It is shown that the ion assistance expands the operating range of the magnetron diode, increases the deposition rate, and substantially shortens the target training time. At the same time, it practically does not affect the ionization processes in the plasma.
TL;DR: In this article, the kinetics of development of strain phenomena in surface layers of solid bodies was studied by the method of decorrelation of speckle images, and the results showed that the process is independent of the density of the speckles.
Abstract: The kinetics of development of strain phenomena in surface layers of solid bodies is studied by the method of decorrelation of speckle images.
TL;DR: A new optical layout for a projection objective for projecting images formed by digital micromirror devices and liquid-crystal devices in projection information-display systems is proposed.
Abstract: This paper proposes a new optical layout for a projection objective for projecting images formed by digital micromirror devices and liquid-crystal devices in projection information-display systems. The optical layout contains two aspheric lens elements. The optical characteristics and graphs of the residual aberrations are presented for the projection objective that has been calculated.