Explore the vast range of titles available.

Raman spectroscopy is a promising method for analyzing natural gas due to its high measurement speed and the potential to monitor all molecular components simultaneously. This paper discusses the features of measurements of samples whose composition varies over a wide range (0.005–100%). Analysis of the concentrations obtained during three weeks of experiments showed that their variation is within the error caused by spectral noise. This result confirms that Raman gas analyzers can operate without frequent calibrations, unlike gas chromatographs. It was found that a variation in the gas composition can change the widths of the spectral lines of methane. As a result, the measurement error of oxygen concentration can reach 200 ppm. It is also shown that neglecting the measurement of pentanes and n-hexane leads to an increase in the calculated concentrations of other alkanes and to errors in the density and heating value of natural gas.

Photo-controlled or photo-regulated molecules, especially biologically active and operating in physiological conditions, are in steady demand. Herein, furocoumaric and furocoumarinic acids being (Z/E)-isomers relative to each other were obtained in two stages starting from psoralen: the alkaline solvolysis of psoralen led to furocoumaric acid, which was further Z → E photoisomerized (365 nm) to furocoumarinic acid. The kinetics of Z → E photoisomerization was monitored by HPLC and UV-vis spectrophotometry. Photophysical characteristics in the aqueous phase for both acids, as well as the reversibility of (Z/E) photoisomerization process, were also assessed. Furocoumarinic acid was found to be visibly fluorescent at pH 2.0–12.0, with the maxima of fluorescence emission spectra being pH-dependent. The reverse E → Z photoisomerization predicted by quantum chemistry calculations as energetically favorable for the monoanionic form of furocoumarinic acid was proved in the experiment while being complicated by pyrone ring closure back to psoralen in acidic and neutral conditions. The preparative synthesis of furocoumarinic acid outlined in this work is particularly valuable in view of a wide range of pharmacological effects previously predicted for this compound.

This article examines the static and dynamic deformation of the stem of an ear of wheat and of the individual grain. The purpose of the article is to determine the factors of influence on the ear of wheat to isolate the grain. Two stages of grain ripening are considered: in the early stage, the grain is attached to the spike by the stem; in the second, there is no stem, and the grain is attached to the ear by the scales. The ear fluctuations are considered within the Euler–Bernoulli bar theory. The developed model divides the study of the dynamics of the stem of an ear and the dynamics of the grain into two stages. The first stage studies the dynamics of the plant as a whole, while the second stage studies the dynamics of an individual grain in a moving system associated with the ear in bending and vertical fluctuation forms. The model of the ear and the grain fluctuation uses the mechanical characteristics of elastic bonds and elastic bodies, which are determined by spring stiffness, elastic moduli, etc. The results show that in the vertical forms of grain fluctuation, the frequency of fluctuation is much higher than in the bending ones. This article presents the natural fluctuation frequencies of grain at full ripeness and in the early phases of maturation, at which point it is released from the ear.

The work is devoted to the study of the dynamics of the grain mass in a field stripper for grain separation. At the first stage, a model of the movement of the air mass in the considered installation is built and based on a mathematical model that takes into account the turbulence of the movement of the air mass, using the method of finite volumes in the ANSYS package, the field of velocities and pressures is calculated. At the second stage, the movement of a fragment of the grain mass in this flow is considered, its trajectory is built taking into account the interaction with the upper deck of the installation. The performed calculations allow us to choose rational geometric and kinematic parameters at which no stagnant zones appear in the chamber, the grain mass interacts with the upper one, which contributes to the release of grain in the installation chamber.

Mathematical and computer finite element model in the ACELAN package of resonant impact on a spike was developed and a full-scale experiment was carried out. Two installations are considered, one based on a cantilever, the free end of which acts on the spike, and the second is a semi-passive round bimorph. Excitation of vibrations is carried out using an actuator based on piezoceramic elements. In the first installation, low-frequency vibrations of the stem with a spike are excited and the resonance frequency is determined at which only an spike with grain performs intense vibrations. The second installation is designed to excite high-frequency vibrations at which resonant movements of the grains themselves arise. The purpose of both installations is to separate the grain from the spike using resonance phenomena.

The NOAA Wide-Swath Radar Altimeter (WSRA) uses 80 narrow beams spread over ±30° in the cross-track direction to generate raster lines of sea surface topography at a 10-Hz rate from which sea surface directional wave spectra are produced. A ±14° subset of the backscattered power data associated with the topography measurements is used to produce independent measurements of rain rate and sea surface mean square slope at 10-s intervals. Theoretical calculations of rain attenuation at the WSRA 16.15-GHz operating frequency using measured drop size distributions for both mostly convective and mostly stratiform rainfall demonstrate that the WSRA absorption technique for rain determination is relatively insensitive to both ambient temperature and the characteristics of the drop size distribution, in contrast to reflectivity techniques. The variation of the sea surface radar reflectivity in the vicinity of a hurricane is reviewed. Fluctuations in the sea surface scattering characteristics caused by changes in wind speed or the rain impinging on the surface cannot contaminate the rain measurement because they are calibrated out using the WSRA measurement of mean square slope. WSRA rain measurements from a NOAA WP-3D hurricane research aircraft off the North Carolina coast in Hurricane Irene on 26 August 2011 are compared with those from the stepped frequency microwave radiometer (SFMR) on the aircraft and the Next Generation Weather Radar (NEXRAD) National Mosaic and Multi-Sensor Quantitative Precipitation Estimation (QPE) system.

The perspective ways to improve the strength properties and resistance to hydrogen induced cracking (HIC) of low-alloy pipe steels were established. The possibility to improve the strength properties and resistance to HIC of plates due the additive of 0.15% molybdenum while decreasing finish temperature of accelerated cooling from 560 to 420°C was found. The influence of heating in the α-, (α+γ)and γ-regions followed by air cooling on the mechanical properties and resistance to HIC of various alloying systems pipe steels plates was studied. The possibility of increasing the strength while maintaining the resistance to HIC of plates by tempering at heating in the α-region was shown.

About a third reserves of the natural gas and oil contain H2S impurities, which, in the presence of moisture, form an acidic medium and can lead to pipeline destruction by the mechanisms of hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC). With the growing number of hydrocarbon fields being developed with a high content of H 2 S, the demand for gas and oil large diameter pipes grade from ВМS to Х70MS with high resistance to HIC and SSC increases. Comprehensive studies have been carried out in laboratory and industrial conditions to determine the effect of the chemical composition and thermomechanical processing on the microstructure, mechanical properties and resistance to HIC of rolled plates from low-alloy pipe steels. Optimal concentration of segregating elements (С ≤ 0.06%, Mn ≤ 1.00%), and schedules of accelerated cooling after controlled rolling (Т sc ≥ Ar 3 ; Т fc = 520±30°C; V c ≥ 20°C/с) provide the high resistance to destruction in H 2 S-containing media due the formation of a homogeneous microstructure without developed central segregation heterogeneity was determined. According to the research results, the technology for manufacturing of plates for large-diameter pipes grade X52MS, X56MS, X60MS, and X65MS ordered for sour service was developed.

The influence of the shell material (copper and silicon carbide) on the detonation process in cylindrical high explosive charge is experimentally and numerically investigated. We observed the significant differences of wave pictures in the detonation products and in the shells, which were due to differences in the sound velocities in the shells and rapid destruction of the ceramic shell under explosion loading. The specific features of a wave picture at the interface HE/ceramics due to desensitization of explosive under loading by an advanced wave in the shell were detected. Those features lead to decreasing of detonation pressure, blurring of the detonation front, and to increasing of mass velocity behind detonation front that is typical for under-compressed detonation. On the symmetry axis of HE charge in the ceramic shell behind the detonation front the long zone with practically constant pressure was observed. We have identified the mechanism of transmission of disturbances from the periphery to the symmetry axis of the HE charge. The source of the emergence of this zone is identified as transverse waves propagating directly behind the detonation front from the periphery to the symmetry axis of the HE charge.