Arc welding operations are considered to be risky procedures by generating hazardous welding fume for human health. This study focuses on the key characteristics, as well as dispersion models, of ...welding fumes within a work zone. Commercial and widely used types of electrodes with various types of covering (rutile, basic, acidic and rutile-cellulose) were used in a series of experiments on arc welding operations, under 100 and 150 amps of electric current. According to the results of this study, maximum levels of pollution with particles of PM
fraction occur in the workspace during arc welding operations. Disregarding the types of electrodes used, the 3D models of dispersion of the РМ
particles at the floor plane exhibit corrugated morphologies while also demonstrate high concentrations of the РМ
particles at distances 0-3 m and 4-5 m from the emission source. The morphology of these particles is represented by solid and hollow spheres, 'nucleus-shell' structures, perforated spheres, sharp-edged plates, agglomerates of the tree-like (coral) shape. At last the bifractional mechanism of fume particle formation for this type of electrodes is also shown and described. In this article results are reported, which demonstrate the hazards of the arc welding process for human health. The results of the characterization of WFs reported improve our understanding of risks that these operations pose to human health and may strengthen the need for their control and mitigation.
The results of a study of the radial distribution of the mechanical stresses, oxygen concentration, and optical inhomogeneity in antimony-doped germanium crystals 200 mm in diameter, with the ...electrical resistivity ranging from 10.5 to 18.5 Ω cm and grown by the Czochralski method, are presented. It has been established that the residual stresses calculated from X-ray diffraction data are correlated with the results of numerical simulation of thermoelastic stresses and are interrelated with the values of the optical inhomogeneity and the concentration of the dissolved oxygen present in germanium in an atomically dispersed state.
Data on the production of antiprotons at an angle of 40° in the laboratory system in collisions of 50-GeV protons with C, Al, Cu, and W nuclear targets have been obtained in the SPIN experiment ...(IHEP, Protvino, Russia). Invariant cross sections have been measured at transverse momenta up to
p
T
≈ 2.6 GeV/
c
. The an-alysis of the momentum spectra has shown that multinucleon (multiquark) configurations inside a nucleus are involved in the production of antiprotons.
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A process has been developed for the fabrication of double-layer silica ceramic crucibles with a composite inner layer containing 25 wt % boron nitride. We have studied the wettability of the ...container material by molten germanium in an argon atmosphere at a temperature of 1000°C. The contact angle has been determined to be 128°, exceeding that of BN-free silica ceramics by ~8°. The work of adhesion evaluated from the contact angle is 0.25 J/m
2
.
Both Sb-doped Germanium and Ge-Si solid solution single crystals with resistivity from 1.5 to 7 Ω·cm were grown using the Czochralski method. The optical transmission of single crystals and the ...stability of their optical properties were studied by infrared Fourier spectroscopy at a wavelength of 10.6 μm and temperature range from 25 to 60 °C. It was found that decreasing the background impurities concentration leads to the reduction of the infrared absorption at room temperature while not affecting the thermal stability of the optical properties. Thermal stability of the optical properties of Sb-doped germanium single crystals increases by adding from 0.2 to 0.8 at % of silicon.
The laws of germanium(IV) adsorption by adsorbents based on alumina or silica layer-by-layer modified with polyhexamethylene guanidine (PHMG) and tiron (Al
2
O
3
–PHMG–tiron and SiO
2
–PHMG–tiron) ...were studied. The effects of Lewis acid sites of alumina on the anchorage of modifier reagents and on germanium(IV) recovery are discussed. In contrast to silica, tiron is anchored to unmodified alumina. Germanium(IV) adsorption on the Al
2
O
3
–PHMG–tiron adsorbent is both due to interaction with tiron and due to interaction with the alumina surface, while on SiO
2
–PHMG–tiron, adsorption is solely due to complexation with the reagent followed by the formation of surface compounds of the Ge : tiron = 1 : 3 stoichiometry. Quantitative (99%) recovery of germanium(IV) by the SiO
2
–PHMG–tiron adsorbent is achieved in a pH range of 2.0–6.5, and by the Al
2
O
3
–PHMG–tiron adsorbent in the range from 0.5 M HCl to pH 8.5.
Homogeneous Sb-doped single crystals of Ge–Si solid solutions are grown with a silicon content of 0.2 to 0.8 at %. The optical absorption of single crystals with a resistivity of (2–3) Ω cm is ...studied by IR Fourier spectroscopy at a wavelength of 10.6 μm in the temperature range from 25 to 60°C. It is found that the introduction of silicon into antimony-doped germanium improves the temperature stability of the optical properties of the crystals.
The paper presents the results of modification of the silumin surface layer using a multicycle processing technique which combines the formation of the film (titanium)-substrate (silumin) system and ...the low energy high current pulsed electron beam (LEHCPEB) irradiation of submillisecond duration in one cycle. A KOMPLEX plasma-ion-assisted electron-beam setup (Institute of High Current Electronics SB RAS, Tomsk, Russia) is used for silumin treatment. Titanium is used as an alloying element. The thickness of the deposited film is 0.5 μm in each alloying cycle, the number of which is 1, 5 and 10. Surface alloying includes ion-bombardment cleaning and heating by hot and hollow cathodes of argon plasma discharge, with negative bias voltage supply to the specimen (initial heating up to preset temperature, surface cleaning and activation); plasma-enhanced chemical vapor deposition of metal films (argon is used as a carrier gas); and LEHCPEB irradiation of the film (titanium)-substrate (silumin) system. It is shown that multicycle alloying of the grade АK12 silumin (G-AlSi12, DIN, Germany) with titanium leads to a dissolution of silicon and intermetallic inclusions in the surface layer up to 30 μm thick, the formation of submicro- and nanocrystalline multiphase structure with the microhardness and wear resistance, which are 1.4 and 14.2 times higher than in cast silumin.
Data on the production of positively charged particles emitted at an angle of 40
(in the laboratory frame) with transverse momenta of up to 2.7 GeV
in the interaction of 50-GeV
protons with carbon, ...aluminum, copper, and tungsten nuclear targets are presented. Particular attention is given to studying the production of light nuclear fragments, such as deuterons (
) and tritons (
). An analysis of data on
and
particles gives grounds to state that these fragments arise via a local mechanism of their direct knockout from nuclei. The results were obtained in the SPIN experiment at the Institute for High Energy Physics (IHEP, Protvino).
The effect of modifying with Al2O3 nanofibers on the properties of wall building ceramics based on quartzofeldspathic wastes from the enrichment of copper-molybdenum ores were studied. It was found ...that with 0,6 wt.% of Al2O3 nanofibers addition the strength of ceramics sintered at 1000 °C increases from 38,3 to 58,5 MPa, water absorption decreases from 12,8 to 10,6 %, an increase of the frost resistance was observed.
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