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Abstract: The impurity composition of isotopically enriched germane 70GeH4was studied for the first time by gas chromatography–mass spectrometry. Impurities were separated using capillary adsorption columns: GS-GasPro (60 m × 0.32 mm) packed with silica gel, GS-CarbonPLOT (25 m × 0.32 mm × 0.25 μm) packed with a carbon sorbent, and a column packed with poly(trimethylsilylpropyne) (25 m × 0.26 mm, df= 0.25 μm)). The use of these columns is shown to provide a high resolution of chromatographed substances. Impurities were identified by comparing their mass spectra with the data of the NIST library. Gases forming a part of the atmosphere, C1–C7hydrocarbons, chlorine- and oxygen-containing hydrocarbons, sulfur-containing substances, and homologs and alkyl derivatives of germane were detected in germane. As a result of studying the composition of their mass spectra, the mass spectra of impurities 70GeC3H10and 70GeC4H12, which are absent in the published sources, were obtained and described for the first time. The concentrations of impurities in high-purity germane, as well as their distribution over fractions isolated during the rectification purification of germane, were determined. The limits of detection of the identified substances were 2 ×10–7–1 × 10–4mol %.

Despite the recent advances in bottom-up synthesis of different kinds of atomically precise graphene nanoribbons (GNRs) with very diverse physical properties, the translation of these GNRs into electronic devices remains challenging. Among other factors, the electronic characterization of GNRs is hampered by their complex synthesis that often requires custom-made organic precursors and the need for their transfer to dielectric substrates compatible with the conventional device fabrication procedures. In this paper, we demonstrate that uniform electrically conductive GNR films can be grown on arbitrary high-temperature-resistant substrates, such as metals, Si/SiO2, or silica glasses, by a simple chemical vapor deposition (CVD) approach based on thermal decomposition of commercially available perylenetetracarboxylic dianhydride molecules. The results of spectroscopic and microscopic characterization of the CVD-grown films were consistent with the formation of oxygen-terminated N= 5 armchair GNRs. The CVD-grown nanoribbon films exhibited an ambipolar electric field effect and low on–off ratios, which were in agreement with the predicted metallic properties of N= 5 armchair GNRs, and remarkable gas sensing properties to a variety of volatile organic compounds (VOCs). We fabricated a GNR-based electronic nose system that could reliably recognize VOCs from different chemical classes including alcohols (methanol, ethanol, and isopropanol) and amines (n-butylamine, diethylamine, and triethylamine). The simplicity of the described CVD approach and its compatibility with the conventional device fabrication procedures, as well as the demonstrated sensitivity of the GNR devices to a variety of VOCs, warrant further investigation of CVD-grown nanoribbons for sensing applications.

A mathematical model of heat and mass transfer in vacuum‐oscillating drying of lumber in which the drying process is made up of alternating stages of warming up and vacuum treatment has been developed. At the stage of warming up, it has been proposed to use a superheated steam to intensify heat‐ and mass‐transfer processes and to relax stresses occurring at the stage of vacuum treatment.

Sensitized photooxidation of a series of compounds with an anthracene structure in a block poly(methyl methacrylate) (PMMA) containing a tetrapyrrole pigment (TPP) or anthraquinone dyes as spectral sensitizers, was studied. The values of changes in the molar refraction at ? equal to 441 and 633 nm were determined experimentally. They satisfactorily agreed with the theoretical values calculated from dispersional relationships. The initial quantum yields of the photooxidation (?0ox) of the anthracene compounds were measured both in solution and in PMMA blocks. The lack of correlation between the ?0ox values in the solid polymers and in the liquid solution indicates the dominating role of the polymeric matrix in determining the effectiveness of photooxidation process taking place. In the selection of the optimal polymerization conditions for the synthesis of the polymeric blocks, the values of ?0ox of certain anthracene compounds can be up to 1. In the series of the anthraquinone dyes used, 1,4-dihydroxy and 2-aminoanthraquinones, whose ?0ox reaches the values of 0.2–0.25 have the highest sensitizing ability.

The drag of a flat wedge in a subsonic two-phase flow is investigated. In contrast to earlier work of Balanin and Zlobin [1] particular attention is devoted to the influence of the particle size. Detailed investigations are made of the dependences of the forces and aerodynamic coefficients on the concentration of the solid phase, the opening angle of the wedge, and the particle size. It is established that the drag coefficients depend on the particle size only for particles with diameters less than 30 um.

Conclusions It was found that the North-Onezhsk bauxites are promising raw materials for the production of highly resistant ladle bricks.

Abstract: The results of measurements of the drag of axisymmetric bodies with smooth and ribbed central cylindrical sections and affinely similar trailing edges of various lengths are given. The experimental data were obtained for zero angle of attack and the numbers M=0.25–0.85 and Re=107–2.4�107 (calculated on the basis of the length of the body without the trailing section). The trailing-edge flow separation was visualized by the oil film method. It is shown that ribbing can lead to a decrease in drag due not only to a reduction in turbulent friction but also to reduction of the separation zone on the smooth trailing section of the body.

The results of comparative gravimetric measurements of the total drag on an axisymmetric body with a smooth and ribbed cylindrical surface are described. The experiments were carried out in a closed wind tunnel at initial tunnel circuit pressures equal to 0.5 and 1 absolute atmosphere with artificially generated model boundary layer turbulence. The free-stream Mach number was varied on the range from 0.15 to 0.85, the Reynolds number Re, calculated from the model length, on the range 4·106–30·106, and the angle of attacka on the range from 0 to 12°. The maximum total drag advantage obtained with the ribbed model was 8%. A significant fraction of the drag reduction achieved may be associated with the effect of the ribbing on the drag created by the smooth tail of the body.

Abstract: The possibility of reducing turbulent friction with the help of large-eddy-breakup devices (LEBUs) and riblets is studied experimentally. The tests were conducted in a low-turbulence wind tunnel on a flat plate for 2·106le Re le 7·106. The local friction coefficient was measured using internal strain-gauge balances, and the total drag was estimated by the momentum-transfer method. It is shown that a combination of LEBUs and riblets makes it possible to reduce the total turbulent friction drag of a flat plate 1800 mm long by 16%. The effects of the length of a ribbed surface on the efficiency of friction reduction and of LEBUs and riblets on the structure of a turbulent boundary layer are analyzed.

The results of balance aerodynamic tests on model straight wings with smooth and ribbed surfaces at an angle of attack α=−4°–12°, Mach number M∞=0.15–0.63, and Reynolds number Re∞=2.4·106–3.5·106 are discussed. The nondimensional riblet spacings+, which determines the effect of the riblets on the turbulent friction drag, and the effect of riblets on the upper and/or lower surface of a straight wing on its drag, lift, and moment characteristics are estimated.

The possibilities of reducing the drag in pipes with a circular cross section by lining them with riblets have been investigated experimentally for developed turbulent air flow. The maximum drag reduction of 6–7% in the riblet-lined as compared with the smooth pipe was obtained for a dimensionless riblet pitch, expressed in law-of-the-wall parameters,s+=14−18.

A low-turbulence wind tunnel has been used to make an investigation by the weight method of the influence of downwash of the free stream relative to the direction of ribs on the reduction of the frictional drag of a ribbed surface. It was found that an increase of the downwash angle to 10–15° hardly reduced the efficiency of the ribbing. The effect of a relative bluntness ?/s of the crests (s is the ribbing step) of the riblets on the frictional drag was considered, and an appreciable reduction of the efficiency of longitudinal ribbing was observed for ?/s ˜ 0.05.

The results of a gravimetric investigation of the effect of longitudinal riblets on the friction drag of a flat plate are presented. The experiments were carried out with both natural and artificially thickened developed turbulent boundary layers in a zero-gradient flow.

This paper highlights the main functions of clutch automatic control systems. These are:forced clutch disengagement during gear shifting and when the engine falls below its minimum operating speed;forced clutch engagement under conditions of increasing engine speed or vehicle speed at a preset level or at a definite throttle position;adjustment of clutch friction torque, depending on the control parameter used.To achieve this, a closed-loop automatic control system is required. The system compares control signals with feedback from a selected parameter and generates commands for changing clutch friction torque.At present some automatic clutch systems use either the position of the accelerator pedal (‘Drivematic’ and ‘Guidosimplex’) or engine speed (ACTS) as the control parameter. The feedback parameter in these systems is the position of the clutch drive element. Comparison of the two systems shows that those using engine speed as the control parameter are more advanced, although their design is more complex. Engine speed is also used in the system of automatic electrovacuum friction clutch control (EPS) designed at the Central Automobile and Automobile Engine Scientific Research Institute (NAMI), but the principle of operation is totally different from existing systems. Particular features of this system are as follows:all necessary modes of automatic control are provided by only one multi-function electromagnet acting on the vacuum valve in the clutch actuating servo chamber;the feedback is dependent on the position of the clutch actuator and is provided by a spring acting on the armature of the valve drive electromagnet—the force of this spring changes in proportion to the position of the clutch actuator;clutch friction torque control as a function of engine speed is provided by changing the current strength in the electromagnetic winding—these changes are initiated by the electronic control unit of the automatic control system.To achieve the optimal performance of modern high-speed engines in combination with an automatic clutch system, all elements of the clutch control system must have minimal delay in converting input signals into control signals. This requirement resulted from an investigation of the EPS mathematical model comprising three non-periodic dynamic elements. The same results were experimentally proved when amplitude and phase frequency characteristics of the control system were measured.It was shown in particular that the time constants of dynamic elements must not exceed 0.04–0.06 s. This required the application of a brand new engineering circuit for designing the EPS electronic unit. The EPS system is now in mass production and is standard equipment for some models of small passenger cars manufactured in the former Soviet Union. The system has been patented in the United States, Japan, Germany, Great Britain, France and Italy.

A mathematical model has been developed for the process of removing multicomponent moisture from disperse capillary-porous materials during the second drying period.

Conclusions A method of producing refractories from Kovdor deposit natural baddeleyite concentrate, with the use of natural grain-size powders (less than 0.5 mm) obtained after concentration of the residues of iron ore concentrate, has been developed.

The effect of ribbed coatings and large-eddy-breakup devices (LEBUs) on the turbulent friction and total drag of a body-of-revolution model has been studied in a low-speed wind tunnel.

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Analysis of the literature revealed a lack of filtering centrifuges, which include the difficulty of regenerating the filtering surface. The presented constructive solutions for its elimination provide only local, but not complete regeneration of the filtering surface. The authors investigated the regeneration of filter elements when the blades rotate around the axis as a result of the engagement of parts of the rotary device. In order to exclude shock loads in the process of turning, various cam designs are considered, the best of which is a fork cam.

The paper analyses experimental data obtained in studies of high-temperature treatment of softwood and hardwood in an environment of saturated water steam. Data were processed in the Curve Expert software for the purpose of statistical modelling of processes and phenomena occurring during this process. The multifactorial modelling resulted in the empirical dependences, allowing determining the main parameters of this type of hydrothermal treatment with high accuracy.