The explosive welding process is widely used for fabrication of layered composites. However, many problems connected with microstructure formation near the interface during explosive loading and the ...dependence of composites final properties from fabrication technique and subsequent treatment are unclear. In the present work, we researched feature of interface structure, microstructure and mechanical properties of sandwich composites on base of copper and low carbon steel joined by the explosive welding. Three-layered copper/steel/copper composites have wavy interfaces which were caused by the effect of plates impact collision. Cold rolling was used as additional hardening process of a welded sandwich composites. It was found that wavy interface after cold rolling acquires a waveless profile. According to EBSD analysis, explosive welding and cold rolling with a total reduction of 50% resulted in grain refinement in copper and steel layers due to the development of dynamic polygonization and recrystallization processes. From the results of tensile tests, it was determined that the sandwich composites have higher strength properties as compared to initial copper in 1.8–3.5 times. The high values of impact strength of sandwich composites are attributed to the influence on ductile copper layers and fracture energy dissipation at the expense of crack deviation while crossing the interfaces.
Non-adiabatic motion of plasma sheet protons causes pitch-angle scattering and isotropic precipitation to the ionosphere, which forms the proton auroral oval. This mechanism related to current sheet ...scattering (CSS) provides a specific energy–latitude dispersion pattern near the equatorward boundary of proton isotropic precipitation (isotropy boundary, IB), with precipitation sharply decreasing at higher (lower) latitude for protons with lower (higher) energy. However, this boundary maps to the inner magnetosphere, where wave-induced scattering may provide different dispersion patterns as recently demonstrated by Liang et al. (2014). Motivated by the potential usage of the IBs for the magnetotail monitoring as well as by the need to better understand the mechanisms forming the proton IB, we investigate statistically the details of particle flux patterns near the proton IB using NOAA-POES polar spacecraft observations made during September 2009. By comparing precipitated-to-trapped flux ratio (J0/J90) at >30 and >80 keV proton energies, we found a relatively small number of simple CSS-type dispersion events (only 31 %). The clear reversed (wave-induced) dispersion patterns were very rare (5 %). The most frequent pattern had nearly coinciding IBs at two energies (63 %). The structured precipitation with multiple IBs was very frequent (60 %), that is, with two or more significant J0/J90 dropouts. The average latitudinal width of multiple IB structures was about 1°. Investigation of dozens of paired auroral zone crossings of POES satellites showed that the IB pattern is stable on a timescale of less than 2 min (a few proton bounce periods) but can evolve on a longer (several minutes) scale, suggesting temporal changes in some mesoscale structures in the equatorial magnetosphere. We discuss the possible role of CSS-related and wave-induced mechanisms and their possible coupling to interpret the emerging complicated patterns of proton isotropy boundaries.
The problem of early diagnosis of skin melanoma by dermatoscopic images of skin neoplasms is considered. A model for assessing the diagnostically significant morphological characteristics of neoplasm ...elements—structureless areas—is proposed. An experimental study has been conducted to determine the adequacy of the model. The most informative features for assessment of morphological characteristics have been identified. The best classification accuracy (94%) has been achieved for feature A1. The results of this study can be applied in the development of medical decision support systems for the diagnosis of skin melanoma.
A new method is proposed for activating the vibrojet mixing of heterogeneous components in computer-controlled machines that include a two-rotor vibrational drive with kinematic self-excitation of ...vibration. Simulation of the phase flows in FlowVision software indicates that the two-rotor vibrational mixer is more effective than a single-rotor system. The velocities of the phase flows are determined, and their topological pattern in mixing is presented.
The article considers aspects of leather waste processing aimed at using dispersed waste for creating composite materials of various purposes. It is shown that a reduction in the relaxation and creep ...of the material is achieved by increasing the cutting speed. The proposed method of dimensional dispersion uses a claw-shaped impact cutting tool, the complex movement of which is powered by a high-frequency vibration motor. A model of the process of leather waste dispersion is developed in the LSTC LS-Dyna software for continuum mechanics modeling.
The coating with a porous structure, having a good adhesion to the substrate and containing titanium dioxide in the modifications of rutile and anatase, has been obtained by plasma electrolytic ...oxidation of VT1–0 technically pure titanium in a 0.1 M neutral aqueous solution of Na2SO4. Gold 10-nm-layer has been deposited on surface by electron-beam evaporation to obtain Ti/TiO2/Au composite. This gold layer consists of 5 nm gold nanoparticles, which has been determined based on the coherent scattering regions for the diffraction peak (111) using the Debye-Scherrer method. Deposition of 10-nm gold layer on the surface of Ti/TiO2 results in increase in photocurrent densities from 3·10−9 A/cm2 to 4·10−6 A/cm2. Calculation from the slopes of the Mott-Schottky plots enable one to estimate the number of charge carriers (donors) and the flat band potential vs Ag/AgCl, which are ND = 3.9·1019 cm−3, Efb = – 0.14 V for Ti/TiO2 and ND = 3.0·1020 cm−3, Efb = – 0.4 V for Ti/TiO2/Au composite.
•Ultrathin Au layer has been evaporated on the surface of Ti/TiO2 composite.•A Schottky barrier is formed between the Au nanoparticles and the TiO2.•Au film increases the photocurrent density by three orders of magnitude.
We investigate an unusual sequence and peculiar features of magnetotail changes during a storm‐range substorm initiated by the interplanetary shock. Auroral observations and measurements at several ...favorably distributed magnetospheric spacecraft allowed the construction of an adaptive time‐dependent magnetospheric model to quantitatively characterize the configurational changes and mapping variations. Several passages of low‐altitude spacecraft in polar orbits near midnight help reveal the magnetic configuration of the nightside tail‐dipole transition region. In this event, an intense auroral and convection activity (accompanied by an up to 1,500 nT increase in the SuperMag AL‐index index) emerged in the highly compressed magnetosphere after the passage of interplanetary shock followed by strongly southward interplanetary magnetic field (IMF). This directly driven phase of the activity continued for an hour and resulted in the formation of a hybrid magnetic configuration with dipolarized midtail and stretched field lines in the transition region. Observations of energetic particle isotropy boundary latitudes near midnight are consistent with the modeled magnetic configuration. In concert with a downward turn of the solar wind (SW) flow, and weakening of the IMF driver and convection, an unusual stretching signature of the inner magnetosphere magnetic field was observed as close as at r ∼ 5 to 7 Re; which resulted mostly from an increasing downward tilt of the thin azimuthal current. Classic substorm breakup signatures commenced at fairly low, ∼60° magnetic latitude, deep in the closed field line region, in association with the current sheet upward motion. It was followed by strong stepwise poleward auroral expansion. We discuss how these signatures deviate from standard substorm scenarios and may be potentially imparted by the aforementioned changes in SW flow direction and pressure.
Key Points
Strong substorm with −50 nT storm‐like SymH variation and anomalies in the sequence of dynamical configurational changes of magnetotail
The magnetotail attained a highly stretched configuration, consistent with observed isotropy boundary locations near midnight
Changes of solar wind flow orientation could potentially affect the dynamics of the magnetotail by modifying the instability threshold
We present the results of in situ measurements of 134Cs and 137Cs released from the Fukushima Nuclear Power Plant (FNPP) collected at surface and different depths in the western North Pacific in June ...and July 2012. It was found that 15 month after the incident concentrations of radiocesium in the Japan and Okhotsk seas were at background or slightly increased level, while they had increased values in the subarctic front area east of Japan. The highest concentrations of 134Cs and 137Cs up to 13.5±0.9 and 22.7±1.5Bqm−3 have been found to exceed ten times the background levels before the accident. Maximal content of radiocesium was observed within subsurface and intermediate water layers inside the cores of anticyclonic eddies (100–500m). Even slightly increased content of radiocesium was found at some eddies at depth of 1000m. It is expected that convergence and subduction of surface water inside eddies are main mechanisms of downward transport of radionuclides. In situ observations are compared with the results of simulated advection of these radioisotopes by the AVISO altimetric velocity field. Different Lagrangian diagnostics are used to reconstruct the history and origin of synthetic tracers imitating measured seawater samples collected in each of those eddies. The results of observations are consistent with the simulated results. It is shown that the tracers, simulating water samples with increased radioactivity to be measured in the cruise, really visited the areas with presumably high level of contamination. Fast water advection between anticyclonic eddies and convergence of surface water inside eddies makes them responsible for spreading, accumulation and downward transport of cesium rich water to the intermediate depth in the frontal zone.
•Fukushima-derived cesium-isotopes have been detected in the centers of anticyclonic eddies in the western North Pacific.•Maximal concentrations have been observed in the subsurface and intermediate waters as a result of subduction at the eddies.•The observations have been found to be consistent with simulation based on AVISO velocity field.•Lagrangian diagnostics were used to reconstruct origin of tracers imitating seawater samples collected in the eddy cores.
Colloidal systems in form of emulsions or suspensions are widely used in various of industries including oil-gas fields development industry. Invert emulsions and suspensions are actively applied in ...fields development, including enhanced oil recovery, intensification of oil production, drilling and wells workover. Results of laboratory tests for studying physical properties of heterogeneous systems as an emulsion system with nanoparticles and emulsion-suspension system with nanoparticles are presented in this paper. Having unique physical and chemical properties these systems can be effectively applied in upstream of oil and gas as a water-limiting agent or blocking pack with reversible effect. In framework of this research, laboratory tests for evaluation of the influence of the new systems on filtration characteristics of hydraulic fractures are carried out. Laboratory tests are planned in accordance with requirements of international standards and conducted under the closest conditions to subsurface thermal and pressure conditions of formations STyr Abdylovskoe, SBASh Yugomashevskoe and YuS-2 and YuS-4 of Tortasinskoe oil-gas fields. Based on the results, permeability and conductivity indexes of the models of hydraulic fractures before and after filtration of the new types of colloidal systems are calculated. In order to evaluate an efficiency of the new systems and to study a possibility to regulate its blocking properties an analysis of the impact made by a type and a quantity of nanosized solids on to the blocking properties is carried out. An optimal concentration of nanoparticles in the compositions for a range of formation conditions of particular carbonate and sandstone subsurface reservoirs of oil-gas fields of Russian Federation are represented in this paper.
To address the mechanism and factors controlling the injection of energetic particles to the geostationary orbit (GEO), we analyzed the appearance of injections at the GEO drift shell as observed by ...LANL spacecraft in the cases where the flow bursts and associated transient dipolarization were detected at the entry to the inner magnetosphere, in the high beta plasma sheet region on the nightside between 8 and 13 Re. We analyzed two different data sets, one including Geotail observations in 1995–2005 and another including a set of Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations in 2008–2009. We found that only a small portion of all flow bursts at 8–13 Re were associated with particle injection at GEO but that those injection‐associated flows had smaller values of plasma tube entropy parameter (PV5/3) as well as larger change of magnetic field north‐south component (dBz). This confirms a scenario that the bursty flows at the entry of the inner magnetosphere (8–13 Re) penetrate into GEO and produce there the energetic particles flux increase. According to the bubble theory of magnetotail plasma flows, the probability of the deep plasma penetration critically depends on how stretched the magnetospheric configuration is, and this dependence is statistically confirmed in a large database to be the major factor controlling the occurrence of GEO injections. We suggest using the background plasma tube entropy value in the nightside part of the GEO drift shell as a suitable parameter to predict the probability of particle injection to GEO. One more outcome of this study is that the energetic particle injections cannot reliably serve as a tool to identify the substorm onset times, as has been done in many past studies.
Key Points
Only one third of all flow bursts reaching 10 Re are able to penetrate to GEO
Flow burst penetration to GEO is mainly controlled by magnetotail stretching
Bubble model provides an explanation and prediction of penetration efficiency
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