基于背景扣除的弱吸收信息精确提取方法研究

随着半导体器件的快速发展，基于分子振-转吸收光谱的研究日益深入，以可调谐半导体激光吸收光谱（Tunable Diode Laser Absorption Spectroscopy， TDLAS）为代表的检测技术取得巨大进步，应用领域进一步扩大，已有超过一千类仪器应用于连续监测以及过程控制，每年出售的气体检测仪器占据了红外气体传感检测仪器总数的5%以上，已实现不同领域组分浓度、温度、压力等参数的高精度探测。本文针对仪器开发领域目标吸收信息被完全覆盖的复杂应用环境，利用调制技术将吸收信息转移到高频部分，经过分通道背景扣除和谐波信号归一化处理提取吸收信息。以测量含硫天然气中微量H₂S为例，天然气中CH₄含量超过90%，目标组分H₂S的吸收信息被完全覆盖，将吸收信息转移到1 kHz频率，得到的谐波信号峰值与H₂S浓度呈正相关，线性参数达到0.999 9，实现了弱吸收信号的有效提取，从方法上验证了提取弱吸收信号的有效性，进一步扩展了光学气体传感的应用领域，为仪器开发提供技术保障。     

Analysis of volatile lunar compounds: The study of gas retention time on Carbosieve SIII adsorbent with respect to temperature

This work presents the study of the characteristic retention times on Carbosieve SIII adsorbent for several permanent gases CO₂, CO, CH₄, N₂ with respect to the temperature of cooling of adsorption accumulators. To perform this work, a laboratory model of a gas chromatograph that included all key components of a standard instrument has been designed.     

The results of the space technological experiments performed with the suprconducting and magnetic alloys

On board the orbital complex “Salyut-6-Soyuz” during long-term near 0-gravity space flight the technological experiments on synthesis of the superconducting MoGa₅, MO₃Ga and Nb₃Sn intermetallic compounds by means of liquid-phase diffusion and on bulk crystallization of the hypoeutectic superconducting Pb-Sn alloy and magnetically ordered Gd₃Co and (Gd_0.2Tb_0.8)₃Co compounds have been performed. During the process of the liquid-phase diffusion considerable changes of the formation of the reaction layers (mechanisms, phase composition, thickness, etc.) in the superconducting Mo-Ga and Nb-Sn systems were observed. MoGa₅, Nb₆Sn₅ and NbSn₂ phases were found in the ground-based samples while in the flight samples the formation of MoGa₅, Mo₃Ga, Nb₃Sn and Nb₆Sn₅ phases was observed. As a result of the changes of the phase composition of the diffusion layers in the flight samples two superconducting transitions at 18.3 and 5.7 K were established (only one transition at 6.9K was measured for the ground-based sample) (Savitsky et al., Izv. Akad. Nauk SSSR, Metals5, 224–232, 1982; Zemskov et al., Izv. Akad. Nauk SSSR, Physics49, 673–680, 1985). Considerable increasing of the critical current measured for the Pb-Sn flight sample has been observed (Savitsky et al., Dokl. Akad. Nauk SSSR257, 102–104, 1981; Zemskov et al., 1985). Better homogeneity and crystal structure perfection of the flight Gd₃Co and (Gd_0.2Tb_0.8)₃Co samples have been established by means of the micro-zonde and low-temperature X-ray technique (Savitsky et al., Acta Astronautica11, 691–696, 1984; Zemskov et al., 1985). Different behaviour of the ground-based and flight samples in the process of magnetization and the displacements of the temperatures of the magnetic phase transitions have been observed.     

Physicochemical model of the auroral ionosphere

A physicochemical model of excited polar ionosphere has been presented. The model makes it possible to calculate vertical profiles of concentrations of the following excited and ionized constituents: O₂ ⁺, N₂ ⁺, O⁺(⁴S), O⁺(²D), O⁺(²P), O(¹D), O(¹S), N(⁴S), N(²D), N(²P), NO, NO⁺, N⁺, N₂(A³Σ_u ⁺), N₂(B³П_g), N₂(W³Δ_u), and N₂(B′³Σ_u ^-) and the electron concentration during electron precipitations. The energy spectrum of the electrons at the upper boundary of the ionosphere and concentrations of neutral constituents are the input parameters of the model. A model has been compiled based on available publications and includes 56 physicochemical reactions that influence concentrations of the aforementioned constituents in the polar ionosphere. The method of calculating vertical profiles of the excitation rates of atmospheric gases and proper allowance for the electron-vibrational kinetics in the processes of exciting the triplet states of N₂ are specific features of the presented model. The ionospheric model has been approbated using the results of the coordinated rocket–satellite experiment. The agreement between the modeling results and experimental data best for the time being is achieved.     

Influences of H2O mass fraction and chemical kinetics mechanism on the turbulent diffusion combustion of H2–O2 in supersonic flows

Hydrogen is one of the most promising fuels for the airbreathing hypersonic propulsion system, and it attracts an increasing attention of the researchers worldwide. In this study, a typical hydrogen-fueled supersonic combustor was investigated numerically, and the predicted results were compared with the available experimental data in the open literature. Two different chemical reaction mechanisms were employed to evaluate their effects on the combustion of H₂–O₂, namely the two-step and the seven-step mechanisms, and the vitiation effect was analyzed by varying the H₂O mass fraction. The obtained results show that the predicted mole fraction profiles for different components show very good agreement with the available experimental data under the supersonic mixing and combustion conditions, and the chemical reaction mechanism has only a slight impact on the overall performance of the turbulent diffusion combustion. The simple mechanism of H₂–O₂ can be employed to evaluate the performance of the combustor in order to reduce the computational cost. The H₂O flow vitiation makes a great difference to the combustion of H₂–O₂, and there is an optimal H₂O mass fraction existing to enhance the intensity of the turbulent combustion. In the range considered in this paper, its optimal value is 0.15. The initiated location of the reaction appears far away from the bottom wall with the increase of the H₂O mass fraction, and the H₂O flow vitiation quickens the transition from subsonic to supersonic mode at the exit of the combustor.     

Numerical simulation of effects of the August 11, 1999 solar eclipse in the outer ionosphere

The results of a numerical simulation of such parameters of the topside ionosphere as concentration N _e and temperature T _e of electrons, and concentration n(H⁺) and fluxes along the magnetic field lines Φ(H⁺) of H⁺ ions at an altitude of ～2000 km for the conditions of the August 11, 1999 solar eclipse are presented. The calculations were performed using the Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere of the Earth (GSM TIP). It is shown that during the eclipse, in addition to a region of decreased values of T _e in the Northern Hemisphere and in the magnetically conjugate region in the Southern Hemisphere, regions of electron heating emerge in both hemispheres. Simultaneously, an extended region of decreased values of N _e comes into existence and moves behind the Moon’s shadow. Regions with decreased (down to ～30%) and enhanced (up to ～50%) concentrations of H⁺ ions are detected in the global distribution of these ions.     

Evaluation of Ir/Al2O3, Ir–Ru/Al2O3 and Ru/Al2O3 catalyst performance in a 5 N satellite thruster

Ir/Al₂O₃, Ir–Ru/Al₂O₃ and Ru/Al₂O₃ catalysts with approximately 33% metallic content in mass were prepared in 20 impregnation steps. For the Ru catalyst, two impregnation methods were employed: incipient wetness (chlorinated precursor) and by excess volume (non-chlorinated precursor). For the remaining catalysts, only incipient wetness impregnation was used with chlorinated precursors. Catalyst textural properties were evaluated before and after catalytic tests: metallic grade, specific area, mesopore volume distribution, metallic dispersion, and metallic particle average diameter. Catalysts were tested for hydrazine (N₂H₄) decomposition reaction in a 5 N satellite thruster and their performances were compared to Shell 405 commercial catalyst. Results showed that catalysts containing Ir were similar in performance to Shell 405 commercial catalyst and that the catalyst containing only Ru should not be used in cold starts.     

Radio Occultation Measurements of the Radio Wave Absorption and the Sulfuric Acid Vapor Content in the Atmosphere of Venus

The results of the determination of centimeter ( = 5 cm) radio waves absorption in the radio occultation experiments, carried out using the Venera-15and Venera-16spacecraft, are presented. The altitude distribution of the absorber substance is analyzed. The absorbing layer is shown to exist at altitudes of 64 to 58 km in the near-polar regions of the planet. At middle latitudes such an absorbing layer was not found. In the altitude range from 56 to 46 km the radio wave absorption by the sulfuric acid (H₂SO₄) vapor is observed. The content of the sulfuric acid vapor is shown to increase with decreasing altitude: in the mid-latitude region at altitudes of 56.7 and 53 km it equals 5 and 20 ppm, respectively, and at polar latitudes the same content of H₂SO₄vapor is observed at altitudes of 51.2 and 47 km, respectively. A comparison of these results with the data of radio wave absorption in the = 13 cm band, obtained in the Pioneer Venus Orbiterradio occultation experiments, leads to the conclusion that the obtained values of the sulfuric acid vapor content well agree in the regions of overlap of the data.     

Fine structure of interplanetary shock fronts from the data of the BMSW instrument of the PLASMA-F experiment

The paper is concerned with studying the thickness of fronts of 38 interplanetary shocks detected by the BMSW instrument, which is a part of the scientific payload of the SPEKTR-R spacecraft, which was launched into a highly elliptical orbit in 2011. The main parameters of the interplanetary shocks have been calculated as follows: the ratio of thermal pressure to magnetic pressure before the front β, the angle between the shock front normal and the undisturbed magnetic field θ_Bn, the ratio of the shock propagation velocity to the magnetosonic velocity in the undisturbed region M_ms, and the shock front velocity relative to the Earth. It has been shown that the front thickness determined from the plasma parameters approximately matches the front thickness obtained from the magnetic field measurements and lies between 0.5 and 5 proton inertial lengths. In some events, the oscillations have been observed (upstream and downstream of the shock) in plasma parameters and in the magnetic field data. The length has been found to be between 0.5 and 6 proton inertial lengths for the preceding oscillations and between 0.5 and 10 proton inertial lengths for the following oscillations. The average value of the proton inertial length is 62 km.     

Illumination of the Earth’s ionosphere by the vacuum ultraviolet radiation reflected by the moon

The spectral curve of the flux density of the radiation, which is reflected by the full moon towards the Earth’s ionosphere within a wavelength range of 200–1700 Å, has been presented. This curve is obtained by the approximation of space experiment data available in the scientific literature on the lunar spectral albedo and solar spectrum. Estimates of maximum values of spectral densities of fluxes reflected by the full moon in the neighborhood of wavelengths of ionization of basic ionospheric particles (neutral atoms of H I, He I, N I, O I, and Ar I and ions of He II, N II, O II, Ar II, N III, O III, and Ar III, as well as molecules of H₂, N₂, and O₂) are given.     

Longitudinal dependence of the H<Superscript>+</Superscript> concentration distribution in the plasmasphere according to <Emphasis Type="Italic">INTERBALL-1</Emphasis> satellite data

The paper has presented a study of the dependence of the H⁺ ions concentration in the plasmasphere on geographic longitude. A vast database of measurements of the cold plasma density by the Alpha-3 instrument on board the INTERBALL-1 satellite has been used for the study. Based on these measurements, a dependence of the H⁺ ions concentration in the filled magnetic flux tube in the plasmasphere in the equatorial plane under quiet geomagnetic conditions has been obtained as a function of geographic longitude. Studies have been performed for two seasons, summer and winter. It has been shown that, during the summer in the near-midnight sector, the minimum in the H⁺ concentration falls within geographic longitudes of 270°–315°. The ratio of the concentration of H⁺ ions at various longitudes could reach a factor of three. During the winter, in the near-noon sector, the maximum of the H⁺ ions concentration falls within longitudes of 180°–225°, whereas the concentration ratio could reach a factor of 2.2.     

Verification of the Accuracy of the Magnetopause Empirical Models Using the INTERBALL-1 Satellite Data

A statistical analysis of the shape and location of the magnetopause according to the INTERBALL-1 satellite data for the period 1995–1997 is carried out. The instants of crossing the magnetosphere boundaries obtained by the plasma and magnetic data are compared with computations based on three empirical models, namely, Petrinec and Russel, 1996; Shue et al., 1997; and Shue et al., 1998. The state of the interplanetary medium (dynamic pressure of the solar wind plasma P _d and the B _z component of the interplanetary magnetic field) was determined by the measurements onboard the WIND spacecraft. We estimate the accuracy of the considered models for different groups of boundary crossings: single, multiple with small duration (less than 40 min), and multiple with large duration (more than 40 min). It is demonstrated that the small-scale motions of the boundary (<1R _E) are observed more often in the dayside magnetosphere, especially near the cusp region. Large-scale boundary oscillations (>1R _E) are more common in the tail region of the magnetosphere, namely, its flanks. Various models give similar results: about 50% of all events have deviations by more than 1R _E from the model locations. In some cases, the deviation of the measured location of the magnetosphere boundary from the model prediction may be as large as 5–6R _E for all three models considered, the actual boundary being more often located nearer to the Earth than the result of model computations. The best model is that of Shue et al., 1998, but it does not differ significantly from the other models.     

Characteristics of thermal ion outflows in the polar cap according to data of the <Emphasis Type="Italic">Interball-2</Emphasis> satellite

Characteristics of polar wind fluxes at a height of ∼20000 km measured by the Hyperboloid mass-spectrometer installed onboard the Interball-2 satellite are presented in the paper. The characteristics are presented for the upwelling flows of ionospheric ions H⁺, He⁺, and O⁺ from the sunlit polar cap in the period of solar activity minimum. Orbit segments with minimal precipitation of magnetospheric ions and electrons were preliminarily selected, and the measurements where the fluxes of ions coming from the cusp/cleft were excluded as carefully as possible. Thus, the densities, field-aligned velocities, and temperatures of ions in the regions where fluxes of polar wind could be detected with the maximal probability degree are presented in the paper. It is found that cases when only H⁺ ions are reaching the detector are with high probability the polar wind outflows. Their characteristics agree well with the Tube-7 hydrodynamic model and are as follows: n ≈ 1.5 cm⁻³, V _∥ ∼ 21 km/s; T _∥ = 3500 K, and T _⊥ = 2000 K. In cases when He⁺ and O⁺ ions are also detected, the temperatures are substantially higher than the model ones, and the measured field-aligned velocities of O⁺ fluxes are several times higher than the model ones. Moreover, it was revealed that the polar wind outflows are predominantly observed in the polar cap regions where the polar rain fluxes are very small.     

Estimate of the NO concentration in the auroral region based on emission intensities of 391.4, 557.7, and 630.0 nm

Using numerical modeling, the influence of the NO concentration on the intensity of 557.7 nm emission in aurora caused by electron precipitation has been studied. It has been shown that the O₂ ⁺ NO reaction, which reduces the contribution of the dissociative recombination of the O₂ ⁺ ion into the formation of the ¹S state of atomic oxygen, is the main channel of suppression of the intensity of the emission at 557.7 nm. A method of estimating the NO concentration in the aurora based on the data of photometric measurements of emissions at 391.4, 557.7, and 630.0 nm has been proposed. The method has been tested using the data of simultaneous rocket measurements of emissions at 391.4, 557.7, and 630.0 nm and the NO content in aurora. A good agreement of estimates of the NO concentrations performed by the method to the results of direct measurements has been obtained.     

Large-scale irregularities of the winter polar topside ionosphere according to data from <Emphasis Type="Italic">Swarm</Emphasis> satellites

An analysis of the electron density measurements (Ne) along the flyby trajectories over the high-latitude region of the Northern Hemisphere under winter conditions in 2014 and 2016 has shown that the main large-scale structure observed by Swarm satellites is the tongue of ionization (TOI). At the maximum of the solar cycle (F_10.7 = 160), the average value of Ne in the TOI region at an altitude of 500 km was 8 × 10⁴ cm^–3. Two years later, at F_10.7 = 100, Ne ~ 5 × 10⁴ cm^–3 and Ne ~2.5 × 10⁴ cm^–3 were observed at altitudes of 470 and 530 km, respectively. During the dominance of the azimuthal component of the interplanetary magnetic field, the TOI has been observed mainly on the dawn or dusk side depending on the sign of B _y . Simultaneous observations of the convective plasma drift velocity in the polar cap show the transpolar flow drift to the dawn (B_y < 0) or dusk side (B _y < 0). Observations and numerical simulation of the Ne distribution have confirmed the significant role of the electric field of the magnetospheric convection in the generation of large-scale irregularities in the polar ionosphere.     

Dynamics of ion energy-dispersed structures near the plasma sheet outer boundary

An analysis of energy-dispersed structures of protons and populations of electrons has been made using the Interball-2 satellite data for the apogee parts of 1579 (September 13, 1997) and 1276 (July 2, 1997) orbits. At each orbit, the satellite crossed the auroral zone twice at altitudes of 13500–19000 km moving first poleward (the first crossing) and then equatorward (the second crossing). A transformation of the types of energy-dispersed structures near the outer boundary of the auroral zone was observed at the first and second crossings: VDIS into TDIS (orbit 1579) and TDIS into VDIS (orbit 1276). The VDIS represent solitary structures of 0.3–10 keV consisting of several small-scale structures 2–5 min long, while the TDIS are repeating injections of 1–14 keV 1–3 min long with the repetition period of 2–4 min. It is shown that the VDIS-to-TDIS and TDIS-to-VDIS transformations are distinctly related to the phase of a substorm. The VDIS were observed under magnetically quiet conditions before a substorm or at the recovery phase of a substorm, while TDIS were observed during the main phase of a substorm.     

A Magnetospheric Substorm and the Motion of the Magnetopause

Using a single event as an example, we make an analysis of the time development of a substorm and estimate its influence on the motion of the low-latitude boundary of the magnetosphere. To this end, we compare the data on plasma and magnetic field obtained by five spacecraft (WIND, INTERBALL-1, GEOTAIL, GOES-8, and GOES-9) with measurements made by ground-based stations. It is shown that the release of energy of the geomagnetic tail begins from a disruption of the current sheet near the Earth. The high-speed plasma stream that transfers a magnetic flux to the Earth and can have an effect on the magnetic field configuration near the Earth is detected later. Almost simultaneously with a substorm onset a series of magnetopause crossings has been detected by the INTERBALL-1 satellite on the evening side of the low-latitude magnetosphere. In this paper we consider some of possible causes of this motion of the magnetosphere boundary, including variations of parameters of the solar wind, Kelvin-Helmholtz instability, and substorm processes. It is shown that fast motions of the magnetopause are detected almost simultaneously with field variations in the near magnetotail of the Earth and geomagnetic pulsations Pi2 on ground-based stations. A sufficiently high degree of correlation (K = 0.67) between the amplitude of Pi2 pulsations and the amplitude of magnetic field variations near the magnetopause is probably indicative of the connection of short-term motions of the magnetosphere boundary with the tail current disruption and the process of formation of a substorm current wedge.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 4, 2005, pp. 248–259.Original Russian Text Copyright © 2005 by Nikolaeva, Parkhomov, Borodkova, Klimov, Nozdrachev, Romanov, Yermolaev.     

NiCrBSi+Ni/MoS_2涂层在空间环境下的摩擦学性能

采用激光熔覆技术在TC4合金基体上制备了Ni Cr BSi+Ni/Mo S2复合涂层,考察了该复合涂层在真空、原子氧辐照环境下的表面形貌及元素变化。利用真空摩擦磨损试验机分别完成了干摩擦条件下2种环境的摩擦磨损性能测试。结果表明:Ni Cr BSi+Ni/Mo S2复合涂层经过原子氧辐照后,有部分元素被氧化及化合物分解的现象,但并没有发生明显的材料性能改变以及润滑涂层的破坏。与TC4合金相比,2种环境下该复合涂层均具有良好的润滑减摩效果,证明Ni Cr BSi+Ni/Mo S2复合涂层具有一定的抗原子氧辐照的能力。     

Photochemical initiation of gaseous detonations

Direct initiation of detonations in gaseous mixtures of C₂H₂-O₂, H₂-O₂ and H₂-Cl₂ in the pressure range of 10–150 torr using flash photolysis was studied. Similar to blast initiation using a concentrated powerful energy source, it was found that for photochemical initiation, there exists a certain threshold of flash intensity and energy for each mixture at any given initial pressure and composition below which a deflagration is formed. At the critical threshold, however, a fully developed detonation is rapidly formed in the immediate vicinity of the window of incident UV radiation. However, at super critical flash energies, the amplitude of the detonation formed decreases and combustion of the entire irradiated volume approaches a constant volume explosion. It was found that photo-chemical initiation requires both a certain minimum peak value of the free radical concentration generated by the photo-dissociation as well as an appropriate gradient of this free radical distribution. The minimum peak radical concentration permits rapid reaction rates for the generation of strong pressure waves, while the gradient is necessary for the amplification of the shock waves to a detonation. If the gradient is absent and the free radicals are uniformly distributed in the mixture, then the entire volume simply explodes as in a constant volume process. The present study reveals that the mechanism of photochemical initiation is one of proper temporal synchronization of the chemical energy release to the shock wave as it propagates through the mixture. In analogy to the LASER, the term SWACER is introduced to represent this mechanism of Shock Wave Amplication by Coherent Energy Release. There are strong indications that this SWACER mechanism is universal and plays the main role in the formation of detonations whenever a powerful concentrated external source is not used to generate a strong shock wave in the explosive.     

Ignition system for oxygen/hydrogen auxiliary propulsion systems

When the oxygen/hydrogen bipropellant combination was selected for use in the Space Shuttle Main Engine, it became apparent that many advantages may result if the Auxiliary Propulsion System Engines were to use the same propellants. A new ignition system, possessing a dramatically new level of reliability, durability and response, is required because the oxygen/hydrogen combination is not hypergolic and the projected missions will require a very large number of fast-response engine starts.The objective of this program was to obtain basic data for spark torch ignition methods at operating conditions typical of a Space Shuttle Orbiter Auxiliary Propulsion System. The research included ignition analysis and igniter design, fabrication and hot-fire test.Extensive testing of spark torch igniters was performed (chamber pressure, 206.8 N/cm², 300 psia, nominal) in the Igniter-Only and Igniter-Complete Thruster (thrust, 6672 N, 1500 lbF, nominal) operational modes. Reliable, repeatable ignitions were obtained with spark energies of 1–10 mJ. Hot-fire test results showed there is no effect of back pressure (1.013 × 10⁵ to 1.333 × 10^?2 N/m², 7.60 × 10² to 1 × 10^?4 mm Hg) or low temperature (O₂, 170 K, 306 R; H₂, 107 K, 193 R) on the response of the igniter or the ignition delay of the thruster over the ranges tested. Igniter durability and pulse capability were demonstrated with 150 sec of continuous operation and 1000 consecutive pulses, respectively. Durability was further demonstrated with a series of 2500 Igniter-Complete Thruster ignitions at nominal chamber pressure. No limiting variables were encountered. The hot-fire test results showed the spark torch igniter is capable of meeting fully the typical Space Shuttle Orbiter Auxiliary Propulsion System mission requirements.