A Dual-Wavelength Polarimetric Analysis of the 16 May 2010 Oklahoma City Extreme Hailstorm

A comparative analysis of a supercell hailstorm using simultaneous observations with S-band and C-band polarimetric radars supported by abundant ground-truth reports is presented in this study. The storm occurred on 16 May 2010 and produced a swath of extremely damaging hail across a large portion of the Oklahoma City, Oklahoma, metro area. Hail sizes over 10 cm in diameter and hail drifts upward of 1.5 m in height were reported. Both S-band (KOUN) and C-band [University of Oklahoma Polarimetric Radar for Innovations in Meteorology and Engineering (OU-PRIME)] polarimetric radars in Norman, Oklahoma, sampled the storm at ranges less than 60 km, so that high-resolution dual-wavelength polarimetric data were obtained. At C band, this analysis mostly presents raw Z and ZDR (due to problems with differential phase resulting from an incorrect censoring threshold in the examined case) while taking into account the possibility of attenuation in the interpretation of these data. Among the issues investigated in the study are the relation of hail size measured at the surface to the polarimetric signatures at both wavelengths, the difference between polarimetric signatures at the two wavelengths of hail aloft and near the surface (where melting hail is mixed with rain), and the three-body scatter spike (TBSS) signature associated with large hail

Development of advanced air-blown entrained-flow two-stage bituminous coal IGCC gasifier

Integrated gasification combined cycle (IGCC) technology has two main advantages: high efficiency, and low levels of harmful emissions. Key element of IGCC is gasifier, which converts solid fuel into a combustible synthesis gas. One of the most promising gasifiers is air-blown entrained-flow two-stage bituminous coal gasifier developed by Mitsubishi Heavy Industries (MHI). The most obvious way to develop advanced gasifier is improvement of commercial-scale 1700 t/d MHI gasifier using the computational fluid dynamics (CFD) method. Modernization of commercial-scale 1700 t/d MHI gasifier is made by changing the regime parameters in order to improve its cold gas efficiency (CGE) and environmental performance, namely H2/CO ratio. The first change is supply of high temperature (900°C) steam in gasifier second stage. And the second change is additional heating of blast air to 900°C. © The authors, published by EDP Sciences, 2017.This work was carried out at the Ural Federal University and Science Foundation (project no. 14-19-00524).financially supported by the Russia

Modeling of phase transformations in steel products during cooling process

Методика численного моделирования превращений в процессе охлаждения изделий из металлов и сплавов позволяет с технически приемлемой точностью прогнозировать структуру и свойства готовых изделий после того или иного вида термической обработки (нормализация, закалка и т.п.). Методика является универсальной, т.к. позволяет проводить расчеты по заданному алгоритму для изделий любой формы, сечения, изготовленных из любой марки стали и сплавов. В результате становится возможным для материала определенного химического состава установить параметры режима термообработки для получения необходимой структуры и эксплуатационных свойств готовых изделий без проведения дополнительных экспериментов.Numerical modeling of cooling process and phase transformations in steel parts allows technically accurate predicting of their structure and properties depending on the heat treatment sequence applied (normalization, quenching etc.). The method is universal, as it allows calculations for parts of different design, size and for any steel or alloy grade. As a result, it becomes possible to set optimal heat treatment parameters providing desirable structure and properties of finish products with given chemical composition without time / material consuming experiments.Программа развития УрФУ на 2013 год (п.2.1.2.1

Air–snowpack exchange of bromine, ozone and mercury in the springtime Arctic simulated by the 1-D model PHANTAS – Part 2: Mercury and its speciation

Atmospheric mercury depletion events (AMDEs) refer to a recurring depletion of mercury occurring in the springtime Arctic (and Antarctic) boundary layer, in general, concurrently with ozone depletion events (ODEs). To close some of the knowledge gaps in the physical and chemical mechanisms of AMDEs and ODEs, we have developed a one-dimensional model that simulates multiphase chemistry and transport of trace constituents throughout porous snowpack and in the overlying atmospheric boundary layer (ABL). This paper constitutes Part 2 of the study, describing the mercury component of the model and its application to the simulation of AMDEs. Building on model components reported in Part 1 ("In-snow bromine activation and its impact on ozone"), we have developed a chemical mechanism for the redox reactions of mercury in the gas and aqueous phases with temperature dependent reaction rates and equilibrium constants accounted for wherever possible. Thus the model allows us to study the chemical and physical processes taking place during ODEs and AMDEs within a single framework where two-way interactions between the snowpack and the atmosphere are simulated in a detailed, process-oriented manner. Model runs are conducted for meteorological and chemical conditions that represent the springtime Arctic ABL characterized by the presence of "haze" (sulfate aerosols) and the saline snowpack on sea ice. The oxidation of gaseous elemental mercury (GEM) is initiated via reaction with Br-atom to form HgBr, followed by competitions between its thermal decomposition and further reactions to give thermally stable Hg(II) products. To shed light on uncertain kinetics and mechanisms of this multi-step oxidation process, we have tested different combinations of their rate constants based on published laboratory and quantum mechanical studies. For some combinations of the rate constants, the model simulates roughly linear relationships between the gaseous mercury and ozone concentrations as observed during AMDEs/ODEs by including the reaction HgBr + BrO and assuming its rate constant to be the same as for the reaction HgBr + Br, while for other combinations the results are more realistic by neglecting the reaction HgBr + BrO. Speciation of gaseous oxidized mercury (GOM) changes significantly depending on whether or not BrO is assumed to react with HgBr to form Hg(OBr)Br. Similarly to ozone (reported in Part 1), GEM is depleted via bromine radical chemistry more vigorously in the snowpack interstitial air than in the ambient air. However, the impact of such in-snow sink of GEM is found to be often masked by the re-emissions of GEM from the snow following the photo-reduction of Hg(II) deposited from the atmosphere. GOM formed in the ambient air is found to undergo fast "dry deposition" to the snowpack by being trapped on the snow grains in the top ~1 mm layer. We hypothesize that liquid-like layers on the surface of snow grains are connected to create a network throughout the snowpack, thereby facilitating the vertical diffusion of trace constituents trapped on the snow grains at much greater rates than one would expect inside solid ice crystals. Nonetheless, on the timescale of a week simulated in this study, the signal of atmospheric deposition does not extend notably below the top 1 cm of the snowpack. We propose and show that particulate-bound mercury (PBM) is produced mainly as HgBr₄^2− by taking up GOM into bromide-enriched aerosols after ozone is significantly depleted in the air mass. In the Arctic, "haze" aerosols may thus retain PBM in ozone-depleted air masses, allowing the airborne transport of oxidized mercury from the area of its production farther than in the form of GOM. Temperature dependence of thermodynamic constants calculated in this study for Henry's law and aqueous-phase halide complex formation of Hg(II) species is a critical factor for this proposition, calling for experimental verification. The proposed mechanism may explain observed changes in the GOM–PBM partitioning with seasons, air temperature and the concurrent progress of ozone depletion in the high Arctic. The net deposition of mercury to the surface snow is shown to increase with the thickness of the turbulent ABL and to correspond well with the column amount of BrO in the atmosphere

Induction surface hardening of 42CrMo4 steel tubes designed for rotary percussive drilling equipment

42CrMo4 steel tubes are subjected to multiple induction heat treatments to obtain various hardened layer depths after spray water quenching. Current frequency, induction unit power and coil movement velocity along the tube axis are under consideration. The hardened layer depth is estimated along the transverse direction of the tubes using metallographic studies and microhardness measurements. An empirical equation is obtained for the hardened layer depth as a function of the induction heat treatment parameters. The laboratory test results are employed to develop the technology of the production of 42CrMo4 steel tubes designed for rotary percussive drilling equipment. The service life of induction hardened tubes during abrasive wear resistance field tests is approximately twice as long as that of conventionally nitrided ones. © 2016 Author(s)

Selection of technology for the low calorific synthetic gas combustion in the gas turbine combustion chamber

The leading gas turbines manufacturers are developing the technologies of the environmental friendly combustion of industrial and synthetic gases of low calorific values. In this case they are faced with critical problems concerning combustion stability assurance and the necessity of the gas turbines significant modernization due to the differences between the low calorific and natural gases. The numerical simulation results of the low calorific value synthetic gas combustion in the combustion chamber by means of different technologies are considered in the paper. © The authors, published by EDP Sciences, 2017.This work was carried out at the Ural Federal University and financially supported by the Russian Science Foundation (project no. 14 -19 -050 24)

Study of the two-stage gasification process of pulverized coal at the hydrodynamic flow separation

The paper presents a numerical study of advanced two-stage gasifier with a combined countercurrent and concurrent flow pattern and dry fuel feed system EAGLE. The Kuznetsk coal was used as a fuel for the gasifier under study. We have conducted studies on the influence of the inclination angle of the upper burners in horizontal and vertical planes, and the amount of steam supplied, on heat and mass transfer processes in the chamber as well as on the composition of coal-derived gases. It is shown that the increase in the inclination angle of the upper burners in the horizontal plane allows intensifying the process of two-stage gasification and makes it possible decreasing the height of the chamber without sacrifice of the composition of the coal-derived gases. © Published under licence by IOP Publishing Ltd.Problem statement (section 1 and 2) and results analysis (section 4) were carried out at UrFU and supported by the Russian Science Foundation by Grant 14-19-00524 (M. Chernetskiy and A. Ryzhkov

Shaken Granular Lasers

Granular materials have been studied for decades, also driven by industrial and technological applications. These very simple systems, composed by agglomerations of mesoscopic particles, are characterized, in specific regimes, by a large number of metastable states and an extreme sensitivity (e.g., in sound transmission) on the arrangement of grains; they are not substantially affected by thermal phenomena, but can be controlled by mechanical solicitations. Laser emission from shaken granular matter is so far unexplored; here we provide experimental evidence that it can be affected and controlled by the status of motion of the granular, we also find that competitive random lasers can be observed. We hence demonstrate the potentialities of gravity affected moving disordered materials for optical applications, and open the road to a variety of novel interdisciplinary investigations, involving modern statistical mechanics and disordered photonics.Comment: 4 pages, 3 figures. To be published in Physical Review Letter

The dependency of mechanical properties on the microstructure anisotropy index of some alloyed steels

The microstructure banding of the 4340, 42CrMo4 and 20NC11 alloyed steels is estimated using the approach of the ASTM E 1268 standard. The values of the anisotropy index and microhardness are obtained on the longitudinal specimens at various distances from the center of round steel bars with various diameters. Impact strength values in the transversal and longitudinal directions of the bars are obtained. The correlation of the anisotropy index values and the mechanical properties (microhardness and impact strength) of the steels under consideration is derived. © 2017 Author(s).Research are carried out (conducted) with the financial support of the state represented by the Ministry of Education and Science of the Russian Federation. Agreement (contract) no 14.578.21.0114 27.10.2015. Unique project Identifier: RFMEFI57815X0114

Improving the impact toughness of the Hy-Tuf steel by austempering

The microstructure and mechanical properties of the high-strength Hy-Tuf steel are studied after different heat treatment modes - conventional oil quenching and tempering, austempering in the bainite transformation temperature range. It is shown that the tempering embrittlement of the Hy-Tuf steel can be observed at temperatures ranging between 400 and 500 °C. The highest impact toughness of the studied steel for the case of conventional oil quenching and tempering (1.2 MJ/m2) can be achieved after high temperature tempering (600 °C), which also leads to the deterioration of tensile strength down to 800...900 MPa. The unique combination of high tensile strength (above 1300 MPa), elongation (up to 15%) and impact toughness (1.1 MJ/m2) is obtained after austempering at a low transformation temperature. © 2018 Author(s)