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The current work implemented in DSMC vibrational excited levels of N2 and transitions between the levels as well as the dissociation of nitrogen molecules from different levels. Results show that due to insufficient collisions, the flow around a sphere at 70/75 km altitudes has a high degree of nonequilibrium in the vibrational mode where the ground level is separated from the higher levels. The continuum-level calculation results are different from the work of Candler and the nonequilibrium profile predicted by the discrete-level calculation is also different. [ABSTRACT FROM AUTHOR]

Using the X-ray photoelectron spectroscopy, a comparative analysis of the chemical state and electronic structure of carbon nanotubes (CNTs), which were doped using various approaches was made. Doping of CNTs was carried out directly in the course of their synthesis by using a nitrogen-containing carbon precursor, and by post-synthesis treatment of undoped CNTs with a beam of nitrogen ions with an average energy of∼5 keV. The results obtained showed that the doping of CNTs during synthesis provides a dopant concentration of no more than 3 % at. At the same time, a certain part of nitrogen atoms is embedded in the structure of CNT walls in the form of various electrically active defects, the rest of the nitrogen is represented by molecular nitrogen, which is present in the interwall space of multilayer CNTs, as well as in their internal cavities. Doping of CNTs by treatment with a nitrogen ion beam provides a higher degree of doping (∼ 6% at.). In this case, all nitrogen is incorporated into the structure of CNT walls in the form of electrically active defects in the graphene structure. It is shown that the presence of a large number of oxygen-containing functional groups is observed on the CNT surface after irradiation with nitrogen ions. The formation of such groups is possible both during the ion treatment and during the subsequent storage of irradiated samples in the atmosphere. Such groups are also electrically active sites on the surface of carbon nanotubes. The results obtained indicate that the doping of CNTs with nitrogen using ion irradiation is an effective method for modifying their electronic structure. CNTs doped with nitrogen using ion irradiation showed a more than twofold increase in specific capacity compared to CNTs doped during synthesis. [ABSTRACT FROM AUTHOR]

The tangent-slab approximation is implemented in User Defined Functions of the ANSYS Fluent flow-solver to compute coupled flowfield and radiation phenomena in the flow around a reentry body. The flow around the FIRE II capsule at an altitude of 84.6 km, which enters the Earth atmosphere at a superorbital velocity, is considered to test the functions developed in the study. The numerical results of the computations with and without the flowfield–radiation coupling show that there is a noticeable change in the radiative energy source term if this coupling is taken into account, while the distribution of the vibrational temperature of molecular nitrogen is only slightly affected. The effect of the flowfield–radiation coupling on the surface radiative heat flux at the stagnation point is assessed at about 20%. [ABSTRACT FROM AUTHOR]

In recent years, the atmosphere pressure plasma jet was significant point in plasma physics because of its application in medicine as well as biomedical; therefore, the needing for experimental plasma devices was important to produce non-thermal atmospheric pressure plasmas. In present study, double ring electrodes configuration worked in argon flow to plasma plume employed. The impact of the tube diameter on production efficiency of reactive species was predicted, using three different values of tube diameter of Pyrex tube (1.9, 3, and 6 mm). A sinusoidal AC voltage of 15 kV with 6 kHz employed to ignite the plasma operations. Optical emission spectroscopy (OES) was a simple method to understand the plasma diagnostic such as emission intensity. In addition, OES used to detect the active species. Both the ignition and emission intensity of the plasma in the capillary tube depend on tube diameter. Results showed that the tube diameter play a significant role in discharge ignition and sustaining voltage. The time of breakdown of argon gas to generate plasma increased if the tube diameter increased. The peak intensity of OH, (O II), (Ar II) and excited molecular nitrogen (N2) increased more if the tube diameter decreased. [ABSTRACT FROM AUTHOR]

The results of the study of the aggregative stability of high paraffin oil showed that high molecular nitrogen bases with weakly developed alkyl substitution, added in concentrations close to their content in oil, and oxygen-containing acidic compounds isolated from this oil increase the resistance of asphaltenes to precipitation. Highly alkyled nitrogen bases promote this process. [ABSTRACT FROM AUTHOR]

Non-thermal atmospheric pressure plasma jet can easily be generated via a coplanar-coaxial dielectric (quartz tube) barrier discharge configuration driven by AC high voltage source at 11 kHz frequency in flowing argon gas. The plasma jet was characterized by its physical dimension, electrical and optical emission properties. It was found that smaller diameter of the quartz tube produced jets of shorter length. To generate a jet at maximum length for larger tube diameters, higher gas flow rate was required. Increasing the width of the active electrode also produced plasma jets of longer length. Current spikes superposed on the sinusoidal current waveforms were observed when the active electrode of shorter length was used. These spikes diminished when the width of the active electrode was increased to 15 mm. When the active and ground electrodes were inter-changed in position, no plasma jet was formed externally but upstreaming of the jet was observed. No discharge was ignited when the ground electrode was removed. The spectrum obtained showed emission lines from the second positive system, C³Πu - B³Πg of molecular nitrogen as well as Ar I state. [ABSTRACT FROM AUTHOR]

This work studies the interaction of the DSMC vibrational relaxation models and dissociation of molecular nitrogen at moderate Mach numbers where such processes are important. The total collision energy (TCE) and QCT models for the N2 dissociation reaction were considered and the dissociation from different N2 vibrational excited states was included in the simulations. It was found that the use of the QCT rates compared to the usual, TCE model gave a substantially higher degree of dissociation and smaller shock width due to the non-equilibrium distribution in the vibrational states. [ABSTRACT FROM AUTHOR]

Coherent Rayleigh-Brillouin scattering (CRBS) line shapes have been experimentally and numerically investigated for the first time in the high laser intensity regime (>1×1016 W/m2) for molecular nitrogen at 300 K. All narrowband pumps were used to generate deep, monochromatic potential wells in the experiment allowing for direct comparison with a DSMC numerical approach. Both results show a line shape narrowing compared to previous low intensity CRBS line shape models due to energy and momentum deposition from the laser field to the gas. The DSMC results indicate a temperature increase along the center of the laser pulse of 51 K and an induced bulk motion of 100 m/s. [ABSTRACT FROM AUTHOR]

This paper comprises an analysis of optical emission spectroscopy (OES) techniques and results of their application for diagnostics of middle and low electron densities in low temperature plasmas. The following OES diagnostic techniques based on: 1) line merging along spectral line series, 2) use of line shapes and Stark halfwidths of hydrogen Balmer lines, 3) line shape of helium lines with forbidden components and 4) use of molecular nitrogen bandhead intensities are studied, discussed, tested and applied and in some cases ugraded for electron density measurements. The overall comparative analysis is performed also. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Chemical reactions involving carbon dioxide are prominent in a variety of environments and, therefore, important for modeling reaction pathways and quantifying molecular abundances. In atmospheres and in outer solar system ices, for example, radiation induced degradation of abundant chemical species like ozone, oxygen, carbon dioxide, or molecular nitrogen can liberate high energy oxygen or nitrogen atoms that may react with carbon dioxide. This work presents a study of these reactions where in the carbon dioxide — oxygen atom reaction, two carbon trioxide isomers (C2v and D3h symmetry) were found to form. In the carbon dioxide — nitrogen atom system, the bent OCNO radical was formed. Rate constants have been derived for these reaction pathways and the dynamics of the reactions are investigated. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This report presents the development of a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4).1 Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonal β-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900°C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data that have indicated a complex and slow time dependent phase change to the c-Si3N4 phase. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products; however, the need for a kinetic approach is suggested to combine with the single component solid models to simulate and further investigate the global phase coexistences. [ABSTRACT FROM AUTHOR]

This research investigates the influence of input parameters in the direct simulation Monte Carlo (DSMC) method for the simulation of a hypersonic flow scenario. Simulations are performed using the Computation of Hypersonic Ionizing Particles in Shocks (CHIPS) code to reproduce NASA Ames Electric Arc Shock Tube (EAST) experimental results for a 10.26 km/s, 0.2 Torr scenario. Since the chosen nominal simulation involves an energetic flow, an electronic excitation model is introduced into CHIPS to complement the pre-existing 11-species air models. A global Monte Carlo sensitivity analysis was completed for this chosen scenario and three quantities of interest (QoIs) were investigated: translational temperature, electronic temperature, and electron number density. The electron impact ionization reaction, N + e- N+ + e- + e-, was determined to have the greatest effect on all three QoIs as it defines the electron cascade that occurs post-shock. In addition, molecular nitrogen dissociation, associative ionization, and the N + NO+ N+ + NO charge exchange reaction were all found to be important for these QoIs. [ABSTRACT FROM AUTHOR]

With a focus on optical lattice gas heating, direct simulation Monte Carlo was used to investigate the interaction between molecular nitrogen, argon and methane, initially at 300 K and 0.8 atm, with pulsed, chirped optical lattices. Created from two 700 mJ, 532 nm, flattop laser pulses, the optical lattice parameters simulated are based on published optical lattice-based experiments, to ensure that pulse energies and durations do not exceed published optical breakdown (ionization) thresholds. Resultant translational gas temperatures, as well as induced bulk velocities, were used quantify energy and momentum deposition. To maximize available gas temperature changes achieved using the technique, laser pulses were linearly chirped to produce lattice velocities able to more effectively facilitate energy deposition throughout the pulse duration. From the initial conditions, the maximum, end pulse axial translational temperature obtained in nitrogen was approximately 755 K, at a lattice velocity of 400 m/s linearly chirped at 25 Gm/s² over the 40 ns pulse duration. To date, this stands as the single largest, numerically-predicted temperature change from optical lattice gas heating under the numerical integration of real world energy and laser-based limitations. [ABSTRACT FROM AUTHOR]

With a focus on optical lattice gas heating, direct simulation Monte Carlo was used to investigate the interaction between molecular nitrogen, initially at 300 K and 0.8 atm, and ten successive, pulsed optical lattices in the presence of two multipass cavity concepts. Created from two 5 ns, 130 mJ, 532 nm laser pulses, the optical lattice parameters simulated were chosen based on published optical lattice-based experiments. Similarly, the cavity concepts used were simulated with optical energy losses comparable to that observed experimentally. Translational gas temperatures were sampled on every cavity round trip and found to facilitate several hundred Kelvin increases in some cases. Importantly, these simulation results suggest that while optical energy losses significantly limit attainable gas temperatures in the context of multipass optical cavities, net momentum deposition into the gas profoundly impacts the energy deposition potential and gas temperature changes achievable through optical lattice gas heating. [ABSTRACT FROM AUTHOR]

Studies of equilibrium breakdown were done for two flow problems representative of typical conditions for vehicles reentering the Earth atmosphere. The first studied problem was a 81 km Crew Exploration Vehicle (CEV) re-entry flow, with additional considerations for local flow features along the stagnation line. The second problem was a classical Couette flow, a volume of gas confined between two fast moving parallel plates of indefinite length and width. Both of the problems were solved by the DSMC technique with the particle velocity data collected to compute the distribution function at the areas of interest. In the case of stagnation line flow, a strong shock wave, formed in front of the vehicle at an altitude of 81 km was studied, and in the case of Couette flow, a high velocity boundary layer was examined in details at different Knudsen numbers. For both of the cases the Kolmogorov-Smirnov (K-S) test was applied to determine the degree of local flow non-equilibrium with following considerations regarding the applicability of coupled statistical BGK and DSMC techniques in the semi-rarefied flow regimes where the use of the baseline DSMC is limited due to the computational cost. [ABSTRACT FROM AUTHOR]

The quantitative analysis of spectroscopic data from low temperature plasmas is strongly supported from collisional radiative (CR) modeling. Low pressure plasmas for basic research in the lab and for industrial use have several aspects in common with the cold edge of magnetic fusion plasmas. On the basis of applications of CR modeling for atomic and molecular hydrogen, molecular nitrogen, and diatomic radicals such as CH and C2, the relevance of individual processes for data interpretation is demonstrated for ionizing and recombining plasmas. Examples of such processes are opacity, dissociative excitation, dissociative recombination, mutual neutralization, and energy pooling. It is shown that the benchmark of CR modeling with experimental data can be used to identify problems in the ingoing data set of cross sections and rate coefficients. Using the flexible solver Yacora, the capability of CR modeling of low temperature plasmas is highlighted. [ABSTRACT FROM AUTHOR]

Recent experiments on applications of high-intensity femtosecond pulses for studying multi-photon and tunnel ionization of different gases, including air, are discussed. Mechanisms of non-linear absorption and ionization of pure atomic argon and molecular nitrogen gases by UV femtosecond laser pulses were studied using photogalvanic and photoacoustic technique. The effect of the intermediate Rydberg resonance, its dynamic Stark perturbation and ponderomotive up-shift of the first ionization potential of argon atoms and nitrogen molecules by the intense laser pulses has been revealed by observing an increase of a power slope of ion yield from three to four at increasing laser intensity. The photoacoustic technique was also applied for studying the effect of tunnel ionization of air by IR femtosecond laser pulses with sub-critical peak power in the range of intensity ∼0.5-20 PW/cm2. Saturation of ultrasonic signals at near-atomic laser fields, which is well described by ADK model, is observed. [ABSTRACT FROM AUTHOR]

In the present study, we measure the rotational population in supersonic nitrogen free jets using a REMPI (resonantly enhanced multi-photon ionization) method, which is not influenced by secondary electrons, unlike an electron beam method. Nitrogen ions are detected as a REMPI signal and its spectra depending on the wavelength of an irradiated laser beam are analyzed to measure rotational temperature through the Boltzmann plot. Nitrogen gas expands into a vacuum chamber from a sonic nozzle with a D=0.50mm diameter, setting P0D (P0: source pressure), depending inversely on the nozzle Knudsen number, at 15 Torr-mm or lower. In the case of P0D=15.0, the rotational temperature distribution along the centerline of the jet, measured by Boltzmann plot, coincides with Marrone’s data measured by electron beam fluorescence, and the rotational relaxation rate Zr calculated by the relaxation equation results in 1.3. However, the non-Boltzmann rotational distribution appears evidently in the supersonic free molecular nitrogen flows for P0D≤15 Torr-mm and as a decrease in the P0D, the deviation from the Boltzmann distribution and the partial freezing of the population arise more upstream. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Using Quantum Molecular Dynamics, we study the dissociation of nitrogen oxide (NO) and carbon monoxide (CO) along both the principal and reshocked Hugoniots. We obtain good agreement with experimental data in terms of pressure and density. As the molecules dissociate at high pressure and temperatures, we characterize the myriad of species that form. As NO dissociates along both the principal and reshocked Hugoniot, a significant amount of molecular nitrogen forms. As CO dissociates along the principal Hugoniot, first at low pressures, CO2 forms and large particles form (both polymer chains and rings) that contain both carbon and oxygen. At higher pressures (above 30 GPa), the CO2 dissociates and the particles breakup and form a mixture of CO, atomic carbon, and small transient clusters with lifetimes less than a typical molecular vibrational period. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Numerical and experimental results for a rarefied gas expansion through a thin circular orifice are presented. The orifice flow was used as a calibration test for a torsional thrust stand designed to measure force levels of 10[SUP-6] to 10[SUP-3] N. Molecular nitrogen, argon and helium at room temperature were used as test gases. The mass flux and thrust measurements are compared with the direct simulation Monte Carlo results for Knudsen numbers from 40 to 0.01 and plenum to facility background pressure ratio of 10[SUP3]- 10[SUP7]. Factors that affect the total propulsive force, such as jet backflow and facility background gas penetration of the jet, are analyzed. The measured mass flux and total propulsive force are found to agree well with the DSMC simulation results. [ABSTRACT FROM AUTHOR]

The problem of survival of elongated skin flaps is an urgent problem in the field of regenerative medicine and plastic surgery. The attention of researchers in recent years has been drawn to a strategy based on the use of bioactive molecules. Bioactive molecules are practical tools for regulating cellular processes and are used to control cell differentiation, dedifferentiation and reprogramming. A promising direction in increasing the survival rate of elongated skin flaps is the search and isolation of bacterial metabolites characterized by a complex of therapeutic effects. The purpose of this work is to study the effect of metabolites of the strain Bacillus amyloliquefaciens subsp. plantarum on the course of inflammatory processes and engraftment of an elongated skin flap. A decrease in the area of flap necrotization during aerosol treatment with culture liquid filtrate was shown to decrease by 4.16 and 2.96 times compared with treatment with saline or a reference preparation, respectively. It has been established that the healing of the flap during aerosol application of the filtrate is accompanied by the formation of a superficial thin epidermal eschar in the caudal part, which does not capture the underlying connective tissue dermis, accelerated formation of granulation tissue and increased migration of epithelial cells. The results obtained substantiate the expediency of isolating the metabolites of the strain and further studying the spectrum of biological activity. [ABSTRACT FROM AUTHOR]

In the modern world, the amount of wastewater generated as a result of household and economic activities of people is constantly growing, which requires increased efficiency and cheaper methods of purification [1]. With unpurified or insufficiently purified wastewater, ammonium nitrogen enters surface water objects and contributes to secondary pollution of water reservoirs [2], deterioration of water quality, formation of eutrophication processes, death of biota, etc. [3]. The paper presents experimental studies of biofilm formation from microorganisms-destructors of ANAMMOX-complex on an inert carrier for wastewater purification from nitrogen compounds (organic, ammonium, nitrites and nitrates) in the reactor, where denitrification and anoxide oxidation of ammonium nitrogen to molecular one in the inert condition take place simultaneously. [ABSTRACT FROM AUTHOR]

The article overviews the results of research on the peculiarities of studies of the features of modeling chaotic systems using digital finite-accuracy systems with a fixed point for radar systems. The use of such models allows obtaining robust radar systems, as well as to study the dynamic properties of such systems. Electronic properties of such systems allow using them as a basis for powerful and high-frequency communication systems and other electronic devices whose characteristics are competitive in comparison with existing devices. [ABSTRACT FROM AUTHOR]

The article overviews the experience of technology optimization in the existing wastewater facilities by means of biological treatment upgrade. The authors revealed negative input and output indices on the concentrations of phosphorus (phosphates), suspended matters, BIO5, ammoniacal nitrogen, N-NO3. The article provides the curves for the actual daily average wastewater flow rate at the facilities input. The authors selected a wastewater treatment technology (nitrification - denitrification) involving a deep biological elimination of nitrogen, phosphorous and the refermentation in the preliminary settling tanks. This technology is remarkably different from the existing one. The paper outlines further measures on the selection of the required processing equipment to remove nitrogen and phosphorus. [ABSTRACT FROM AUTHOR]

ZnO is a wide band gap, naturally n-type semiconductor with great promise for optoelectronic applications. To date, however, it has proven difficult to dope p-type, a prerequisite for device fabrication. Nitrogen is widely believed to be one of the most promising dopant candidates, however, experimental results to date have been inconsistent; recent theoretical formation energy calculations have indicated that Nitrogen preferentially incorporates into the ZnO lattice in the form of a N2- molecule at an O-site when a Nitrogen plasma source is used, leading to compensation rather than p-type doping. We show by a combination of X-ray absorption spectroscopy at the N K-edge of plasma-assisted molecular beam epitaxy grown ZnO and ab-initio simulations that in as-grown material, Nitrogen incorporates substitutionally on an O-site where it is expected to act as an acceptor. We have also observed the distinctive formation of molecular nitrogen bubbles upon rapid thermal annealing. These results suggest that effective p-type doping of ZnO with N may only be possible for metastable low-temperature growth processes. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper presents an evaluation of the density distribution in swirling turbulent premixed flames. The measurement principle is based on registration of spontaneous Raman scattering, when the reacting gas flow is illuminated by a laser sheet. Evaluation of 1D and 2D distributions of density and temperature were performed in a laminar Bunsen flame as a test case for validation of experimental technique. Time-averaged 2D images of the scattering during rovibronic transitions of nitrogen molecules were captured in turbulent premixed low-swirl and high-swirl (Re = 5000) propane-air flames in a wide range of equivalence ratio. The obtained density fields are useful for better understanding of heat and mass transfer in swirl-stabilized turbulent flames and for validation of CFD results. [ABSTRACT FROM AUTHOR]

Atmospheric pressure plasma jet system (APPJs) is constructed with simple and low-cost components. A homemade alternating current (AC) is employed to generate a high voltage from (0 to 12) kV and a frequency of (0 to 12) kHz ,it is sufficient to ionize the argon gas. The system is a double ring electrodes configuration. Pyrex tube is used as a discharge of a barrier, its characteristics are 140 mm length and the wall thickness is 0.90 mm. The internal and external diameters are 3.2 mm and 5 mm respectively. A double-ring configurations made of aluminum cover the outer Pyrex tube. The ring electrodes have 0.1 mm thickness and 10 mm width. The distance between the electrodes is 12 mm and the distance between the ground electrode and the nozzle of the Pyrex tube is 3mm. The behavior of plasma jet length and gas temperature is investigated at different applied voltage and gas flow rate. Optical emission spectrometer (OES) is used to estimate the electron temperature Te and the electron density ne by using Boltzmann plot method. The gas temperature decreases as the flow rate of argon increases but the temperature increases with the applied voltage. The plasma temperature is confined between (22-31)°C and the maximum plasma jet length is 4.2cm. The estimated electron temperature is less than 1 eV and electron density is 1.57×1013 cm-3. This result demonstrates that, the device under consideration is a type of non-thermal plasma and it is suitable to use in biomedical applications. [ABSTRACT FROM AUTHOR]

In this paper, we propose a numerical method for solving the problem of the propagation and gorenje of a methane jet in an axisymmetric satellite air flow. Dimensionless equations of the turbulent boundary layer of reacting gases in the Mises coordinates are used for modeling. To solve the problem in the Mises coordinates, a two-layer, six-point implicit finite-difference scheme is used, which provides a second-order accuracy of approximation by coordinates. Due to the nonlinearity of the equations of conservation and transfer of substances, an iterative process was organized. Separate results of the computational experiment are presented. Comparison of the calculation results for the change of the axial flow temperature according to k−ε and Prandtl models of turbulence and experimental data. [ABSTRACT FROM AUTHOR]

The paper is devoted to a study of the phase composition of bimetallic FePt nanoparticles synthesized by the co-reduction of precursor solutions by an alkaline solution of hydrazine hydrate. XRD structural analysis revealed the solubility limit of the components in a solid solution of a nanostructured Fe-Pt system (about 10 mol.% Fe). It was found that there was a difference between the molar fraction of iron determined by the XRD method and elemental analysis. Such a phenomenon made it possible to put forward an assumption about the existence of a diffraction-invisible part in the system under study. [ABSTRACT FROM AUTHOR]

The study considered catalytically active systems in the synthesis of olefins below DME based on Zn-Zr-Cu*HSZ*Al2O3. The hydrogen form of zeolite (H+) was obtained by burning at 500 ℃ for 4 h. The catalysts were obtained by mixing HSZ-26 with a binder - aluminum oxide suspension and by further forming in extruders. Modification was performed with zinc, copper and zirconium compounds. These active elements have been identified as the most promising for the creation of industrial catalysts. For each element, the most optimal method of introducing it into the catalyst was determined. Catalyst tests were carried out in a device with a flow-type reactor at a temperature of 320-380 ℃ and atmospheric pressure. The loading of the catalyst in the reactor was 3-10 cm3. DME was used as the starting raw material; DME diluent - nitrogen and / or water vapor and methanol. The concentration of DME in the initial gaseous mixture is 10 to 75 % by vol., and that of methanol is 10 to 30 % by vol. The volumetric velocity of the initial gas mixture delivery was changed in the range of 2000-15000 h-1. According to the first high-temperature treatment of zeolite, it was carried out in an air atmosphere at a temperature of 750 ℃ for 4 hours. The treatment of catalysts with water vapor at 500 and 750 ℃ was carried out in a flow-type device according to the method described. IR spectroscopy, X-ray phase analysis, benzene adsorption methods were studied by pre-processing and subsequent structural characteristics of the original zeolite and modified samples, the acidic properties of the catalysts - temperature- programmed desorption of ammonia. [ABSTRACT FROM AUTHOR]

Atomic oxygen and molecular nitrogen are the major constituents in the residual atmosphere at low Earth orbital altitudes, and they collide with spacecraft surfaces at relative velocities of ∼7.8 km s-1. The energy associated with these hyperthermal collisions is in excess of many bond dissociation energies and may help promote materials degradation by allowing barriers to reaction or to collision-induced dissociation (CID) to be overcome. Spacecraft in low Earth orbit (LEO) are also exposed to high fluxes of vacuum ultraviolet (VUV) radiation, which may degrade materials through various photochemical mechanisms. Fluorinated ethylene-propylene copolymer (FEP Teflon®) is commonly used on spacecraft. Many researchers have studied the individual and/or combined effects of atomic oxygen, VUV light, and CID on FEP Teflon®, yet the detailed degradation mechanisms of FEP Teflon® in LEO are still a subject of debate. Although not as ubiquitous as a spacecraft material, polymethylmethacrylate (PMMA) has been studied as a model and control polymer because of its well known propensity to “unzip” upon exposure to VUV radiation. A combination of beam-surface scattering, quartz crystal microbalance (QCM), and surface-recession experiments were conducted to study the effects of various combinations of O atoms (in the ground O(3P) state), Ar atoms, and VUV light on FEP Teflon® and PMMA. A laser-breakdown source was used to create hyperthermal beams containing O and O2 or argon. A deuterium lamp provided a source of VUV light. O atoms with 4 eV of translational energy or less did not react with a pristine FEP Teflon® surface. Volatile O-containing reaction products were observed when the O-atom energy was higher than 4.5 eV, and the signal increased with O-atom energy. Significant FEP Teflon erosion (∼20% of Kapton® H) was observed when it was exposed to the hyperthermal O/O2 beam with an average O-atom energy of 5.4 eV. FEP Teflon® and PMMA that were exposed to VUV light alone yielded volatile products and mass loss. Similarly, CID by Ar also yielded volatile products and mass loss, when the Ar energy was higher than 8 eV. However, the erosion caused by VUV light and/or CID is not significant compared to that caused by O/O2. There were no observed synergistic effects of VUV light and O/O2 exposure. [ABSTRACT FROM AUTHOR]

Atmospheric absorption may have a huge impact on the sonic boom annoyance by reducing the amplitude and increasing the rise time. However, the standard absorption due to the vibrational relaxation of molecular nitrogen and oxygen does not estimate the influence of clouds where scattering by water droplets occurs. As clouds cover more than 50 % of the Earth surface, their influence on sonic boom needs estimation. Test flights performed in the former Sowiet Union in 1967–1968 indicate a strong impact. An existing model for acoustical propagation in a polydispersed air-vapor-droplet suspension is reviewed. It takes into account energy and viscous momentum transfer as well as evaporation processes influenced by diffusion of vapor through the air. When applied to the conditions prevailing in atmospherical clouds, it shows a dramatical increase of sound attenuation and dispersion. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The process of ignition and subsequent combustion of the solid-phase product (carbon residue) of the steam gasification of oil sludge waste (OS) was studied, its physical and chemical characteristics were determined, and the energy applicability was evaluated. It was found that the product is characterized by a high content of ash (Ad = 70 wt%) and sulfur (Sd = 1.7 wt%). The lower heating value was 14.2 MJ/kg. According to the thermal analysis data, the initial and final temperatures of intensive oxidation were 248 °C and 518 °C, respectively. The ignition delay time exponentially decreased by 67% with increase in the temperature of the heating medium (from 500 to 700 °C). The combustion process at Tg = 700 °C was accompanied by the formation of flame near the fuel sample. [ABSTRACT FROM AUTHOR]

Three-dimensional Navier–Stokes computation of non-equilibrium ionized airflow around the RAM-C II capsule is performed for different flight altitudes. The numerical simulation is performed using one-temperature and multi-temperature approximations. Numerical results show non-symmetrical behavior of macroparameters on windward and leeward sides. Both approximations provide a good agreement between computed peaks of electron densities around the capsule and in-flight data. [ABSTRACT FROM AUTHOR]

The features of supersonic clustered flows measurements using molecular beam mass spectrometry are considered. The results of unusual density distributions on the molecular beam axis with varying nozzle – skimmer distances, as well as transverse density distributions in the beam at fixed distances from the nozzle are presented. It is shown that a sharp drop in the density of the monomeric component near the molecular beam axis, which was not previously detected by other experimenters, is due to a sharp separation of the clustered flow composition under molecular beam formation. The roles of the skimmer interaction and of heavy clusters mainly presens on the molecular beam axis was discussed. [ABSTRACT FROM AUTHOR]

In this work composite based on multi-walled carbon nanotubes (MWCNTs) and manganese oxide (MnO2/MWCNTs) were studied as the basis material for electrodes of supercapacitors. The structure and chemical state of the formed composites were studied using the method of X-ray photoelectron spectroscopy (XPS). The electrochemical characteristics of the electrodes made based on carbon nanotubes, as well as the MnO2/MWCNTs composite, were carried out by the method of cyclic voltammetry (CV) using a three-electrode electrochemical cell. It is shown that the electrode made on the basis of the composite has a higher specific capacity in comparison with the electrode based on multi-walled carbon nanotubes. An increase in the specific capacitance of the composite-based electrode is provided by redox reactions involving manganese oxide, as well as functional groups that form on the surface of multi-walled carbon nanotubes during the formation of the composite. [ABSTRACT FROM AUTHOR]

The composition and structure of nitrogen-containing bases isolated from the maltene fraction of the liquid products of conversion of asphaltenes of bituminous oil from the Ashalchinskoye oilfield in a supercritical hexane stream at 450°C and 15 MPa are investigated. It is shown that they are represented by a mixture of high molecular weight and low molecular weight compounds, where high molecular weight components prevail. Compared to the initial asphaltenes, their mean molecules are characterized by smaller sizes associated with a decrease in the number of structural blocks (ma = 2.3 versus 3.4), in the composition of which the number of saturated cycles is significantly reduced (Rn* = 2.8 versus 6.0). The size of the aromatic core remains virtually unchanged. (Ra* = 2.9 versus 3.4). At the same time, the internal arrangement of aromatic cores in the naphthenoaromatic system of the structural block (Cα* = 4.5 and 5.6) is preserved, which causes a high degree of screening of the nitrogen atom and, as a consequence, thermal stability of the compounds. Using the GC–MS method, C2−C6 quinolines, C2−C4 benzoquinolines, C1 dibenzoquinolines, and C16H33NO, C18H35NO, C18H37NO aliphatic amides have been identified in the nitrogen-containing bases of maltenes. [ABSTRACT FROM AUTHOR]

Optical diagnostic techniques have been employed at a combustion chamber test rig for investigation of the liquid fuel atomization and mixing with air, and of combustion of the fuel-air mixture formed in the flow. Certain characteristics of the kerosene spray and of the kerosene-air mixture combustion have been determined. An axisymmetric single-burner section with a pneumatic atomizer in the flame tube head was investigated at excess air ratios α = 0.9-1.5. The transverse spatial distributions of average kerosene droplet dimensions and the axial component of the average volume flux of the fuel have been measured in the axial cross-section of the mixture flow by using the Particle Shadow Velocimetry (PSV) technique. The results prove the efficiency of the investigated atomizer in the formation of finely dispersed kerosene- air flow with a regular structure which enables the stability of the combustion process. By employing Coherent Anti-Stokes Raman Scattering (CARS) during combustion of the produced kerosene-air mixture the statistical characteristics of "instantaneous" local gas temperature fluctuations in the flame and transverse distributions of average temperatures in the flame axial cross-section have been measured. The results demonstrate reasonable temporal stability of the obtained kerosene-air mixture combustion over the measurement period, and the possibility to describe the transverse flow structure and its modifications with the flow composition. The set of the complementary data provided by the PSV and CARS techniques at different excess air ratios characterizes the operation of the combustion chamber and expands the variety of possible flame tube head tests. [ABSTRACT FROM AUTHOR]

The ignition process of a syngas/air mixture is considered by means of the experimental technique based on a low-pressure flow reactor equipped with the glow discharge cell and the kinetic modelling allowing for the non-equilibrium excitation of the electronic and vibrational states of oxygen and nitrogen molecules. Glow discharge product vibrational and translational temperatures were determined using Coherent Anti-Stokes Raman Spectroscopy (CARS). The experimental data were used to measure the induction length change that occurred due to the exposure of air to the discharge. The modelling procedure accounted for the measured vibrational temperature of the afterglow species to determine the initial conditions of the investigated mixture at the reactor inlet (at the end of the supply tube). The exceed of the nitrogen vibrational temperature up to 1500 K above the oxygen vibrational and translational temperature, which was below 400 K, was registered at the reactor inlet. The induction length shortening by 10 to 30 % was detected depending on the discharge current and the reactor temperature. The reduction of induction delay time obtained in the simulations has demonstrated qualitative coincidence with the experimental data enabling to employ the developed approach to the study of non-equilibrium combustible mixtures. [ABSTRACT FROM AUTHOR]

The effects of surface chemical processes on the aerothermodynamics of a blunted body are numerically studied by the Direct Simulation Monte Carlo method under typical conditions of spacecraft re-entry into the upper layers of the atmosphere (Knudsen number 0.01). A recently developed model of surface physical and chemical processes with allowance for multiple re- action channels is used in computations. The results of the present study demonstrate a significant contribution of surface chemistry to the heat flux toward the body surface. If the surface reactions between non-identical species leading to nitrogen monoxide for- mation are taken into account, the gas composition near the surface is significantly changed and the heat flux noticeably increases. [ABSTRACT FROM AUTHOR]

The different plasma devices generating the cold atmospheric plasma jets were developed and tested. The single plasma jet with the cylindrical and planar symmetry and multijet devices are operated in helium or argon gas flow in surrounding air. The plasma jet can be up to 7 cm length and can be considerably elongated with a plastic flexible tube connected to the device. The interaction of the plasma jet with cancer calls in vitro was studied for different regimes of plasma generation. The optimization of plasma parameters was done in the experiments, in 2D fluid model simulations, and with MTT and iCELLigence assays checking the viability of cancer cells for different plasma regimes. [ABSTRACT FROM AUTHOR]

A numerical simulation of a weakly ionized air flow around the OREX re-entry capsule is performed, aiming at the comparison of the electron density predicted by DSMC and NS computations to the flight data. The NS computations are performed for two approximations: one-temperature and multi-temperature. The one-temperature and multi-temperature electron density profiles are close to each other; however, the other macroparameters are different. The NS electron density profiles agree well with the profile computed by Gupta et al. (1997) using the Viscous Shock Layer model. The computed number density of electrons is consistent with the flight data. The DSMC prediction is closer to the OREX data than the NS results. [ABSTRACT FROM AUTHOR]

The properties of carbon nitride films prepared using chemical vapour deposition (CVD) method is described in this manuscript. The vapour of an organic molecule 2,4,6-Tris(dimethylamino)-1,3,5-triazine (C9H18N6) pyrolysed at 800 °C deposited on quartz substrates (SiO2) have been investigated. The characterisation of films by different techniques such as XRD, Raman, SEM, FTIR and XPS confirm the amorphous nature of the prepared films. The optical characterisation results of films obtained by the diffuse reflectance spectroscopy (DRS) demonstrate that the amorphous carbon nitride films could have potential applications as photovoltaic materials. [ABSTRACT FROM AUTHOR]

The present work reports pressure dependent lattice thermal conductivity of pyrite SiN2, GeN2 and SnN2 using first principles calculations based on density functional theory. The anisotropy, anharmonicity and microhardness properties of pyrite-SiN2, GeN2 and SnN2 were analyzed by determining acoustic wave velocities, Debye temperature and Grüneisen parameter evaluated from derived elastic constants of present study. The high thermal conductivity of pyrite SiN2 along with its known mechanical strength and insulating property suggest that it can be a potential candidate as substrate material for thermal management system in high-power electronic devices. [ABSTRACT FROM AUTHOR]