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Striped texture of submesoscale fields in the northeastern Baltic Proper : Results of very high-resolution modelling for summer season

Zhurbas Victor, Väli Germo, Kuzmina Natalia

Oceanologia

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2022

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No. 64 (1)

1--21

EN

Very high-resolution modelling of the northeastern Baltic Proper shows that preferentially elongated along the flow, submesoscale inhomogeneities of hydrodynamic fields or stripes of the order of 10–20 km in length and 1 km in width, are typical for summer season both in surface mixed layer and for interior layers which are not directly exposed to atmospheric forcing. In surface layer, the presence of stripes is supported by the remote sensing imagery and their vertical extension is comparable with the mixed layer depth (approx. 5–8 m). In the interior layers, the vertical extension of stripes is considerably larger (approx. 10–50 m) and their slopes exceed the isopycnal slope. Four competitive mechanisms of formation of the mesoscale striped texture are considered: stirring of large-scale inhomogeneities by the eddy field, the classic, inviscid adiabatic fluid symmetric instability, the McIntyre instability, and the strain-induced frontogenesis. Based on the instability criteria and the growth rates and geometry of the disturbances, the classic symmetric instability and the strain-induced frontogenesis are probably responsible for the formation of submesoscale striped texture in the surface layer, while in the interior layers, the strain-induced frontogenesis and hypothetically the McIntyre instability can be essential. Stirring of large-scale inhomogeneities by the eddy field could be responsible for formation of striped texture in a passive tracer concentration and in temperature and salinity in the presence of thermohaline gradients on isopycnic surfaces (thermoclinicity), but it does not imply formation of stripes in dynamically active tracers, such as vertical vorticity, horizontal gradients of buoyancy, etc.

2

Deposition time and annealing effects on morphological and optical properties of ZnS thin films prepared by chemical bath deposition

Chabou N., Birouk B., Aida M. S., Raskin J. P.

Materials Science Poland

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2020

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Vol. 38, No. 4

508--517

EN

Nanocrystalline zinc sulfide (ZnS) thin films are prepared on glass substrates by chemical bath deposition (CBD) method using aqueous solutions of zinc chloride, thiourea ammonium hydroxide along with non-toxic complexing agent tri-sodium citrate in alkaline medium at 80 °C. The deposition time and annealing effects on the optical and morphological properties are studied. The morphological, compositional, and optical properties of the films are investigated by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDAX) and UV-Vis spectroscopy. SEM micrographs exhibit uniform surface coverage. UV-Vis (300 nm to 800 nm) spectrophotometric measurements show transparency of the films (transmittance ranging from 69 % to 81 %), with a direct allowed energy band gap in the range of 3.87 eV to 4.03 eV. After thermal annealing at 500 °C for 120 min, the transmittance increases up to 87 %.

3

Deposition time and annealing effects on morphological and optical properties of ZnS thin films prepared by chemical bath deposition

Chabou N., Birouk B., Aida M. S., Raskin J. P.

Materials Science Poland

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2019

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Vol. 37, No. 3

404--416

EN

Nanocrystalline zinc sulfide thin films were prepared on glass substrates by chemical bath deposition method using aqueous solutions of zinc chloride, thiourea ammonium hydroxide along with non-toxic complexing agent trisodium citrate in alkaline medium at 80 °C. The effect of deposition time and annealing on the properties of ZnS thin films was investigated by X-ray diffraction, scanning electron microscopy, optical transmittance spectroscopy and four-point probe method. The X-ray diffraction analysis showed that the samples exhibited cubic sphalerite structure with preferential orientation along 〈2 0 0〉 direction. Scanning electron microscopy micrographs revealed uniform surface coverage, UV-Vis (300 nm to 800 nm) spectrophotometric measurements showed transparency of the films (transmittance ranging from 69 % to 81 %), with a direct allowed energy band gap in the range of 3.87 eV to 4.03 eV. After thermal annealing at 500 °C for 120 min, the transmittance increased up to 87 %. Moreover, the electrical conductivity of the deposited films increased with increasing of the deposition time from 0.35 × 10−4 Ω·cm−1 to 2.7 × 10−4 Ω·cm−1.

4

Effect of vibration and stirring on 90% and 98% hydrogen peroxide

Okroj N., Michalska K., Jakusz B.

Materiały Wysokoenergetyczne

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2018

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T. 10

88--96

EN

The influence of vibration and stirring of 90% and 98% hydrogen peroxide (high test peroxide – HTP) of two different purity levels in accordance with MIL-PRF-16005F, was determined. Testing was conducted in order to evaluate safety of use of highly concentrated solutions of hydrogen peroxide. The influence of vibration on HTP was tested at different frequencies up to 100 Hz. Further testing investigated the influence of stirring HTP, at three different speed values: 2000 rpm, 4000 rpm and 6000 rpm. During both tests, decomposition was determined by measuring concentration loss using density assay. Liquid during the tests was visually inspected for visible signs of decomposition such as: foaming, gas emission, turbidity.

PL

Określono wpływ wibracji i mieszania na 90% i 98% nadtlenek wodoru klasy HTP o dwóch poziomach czystości zdefiniowanych w normie MIL-PRF-16005F. Badanie przeprowadzono w celu oceny bezpieczeństwa stosowania roztworów nadtlenku wodoru o wysokim stężeniu. Został zmierzony wpływ wibracji o częstotliwości do 100 Hz na HTP. W ramach kolejnego badania sprawdzono wpływ mieszania na HTP, gdzie zastosowano trzy różne prędkości mieszania: 2000 rpm, 4000 rpm i 6000 rpm. Rozkład nadtlenku wodoru mierzony był poprzez pomiar stężenia roztworu przy zastosowaniu metody densymetrycznej. Dokonano wizualnych obserwacji roztworu podczas badań pod kątem występowania widocznych oznak rozkładu, jak: pienienie, emisja gazów, zmętnienie.

5

Mechanical Modification of Al-6%Si By Semisolid Process

Sarajan Z.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 3

1689--1696

EN

In this study by semisolid processing of Al-6%Si alloy, it has been found that small additions of Ti-6Al-4V shift the liquidus temperature up and the recalescence decreases. The nucleation event takes place at higher temperatures. Furthermore, the rate at which growth temperature increases is less than that of nucleation temperature and therefore more nuclei form with less potential for growth. In this processing refiner increases the α-Al percentage and reduces globule size. Improvement of mechanical property and microstructure characterization are the main advantages of this study.

6

Schładzanie, przewietrzanie i mieszanie ziarna składowanego w silosach

Bochat P.

Przemysł Spożywczy

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2008

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T. 62, nr 7

35-37

PL

Współczesny magazyn ziarna i realizowana w nim technologia przechowywania musi uwzględniać zagrożenia powodujące wzrost aktywności biologicznej i enzymatycznej gromadzonych surowców. Konsekwencją, bowiem tych procesów może być ubytek masy, spadek zdolności kiełkowania, przegrzanie, rozkład glutenu, gnicie, pleśnienie, rozwój szkodników, powstawanie zapachu magazynowego oraz wzmożona aktywność fermentów skutkujące obniżeniem jakości ziarna. Obecnie stosowane magazyny przechowalnicze coraz częściej stosują w celu wyeliminowania tych zagrożeń takie procesy jak: schładzanie, przewietrzanie czy też mieszanie ziarna.

EN

The contemporary storage site and the storage technology have to consider threats of the increase of biological and enzymatic activities in the grain mass. The consequence of those processes can be the mass decline, the loss of sprouting abilities, the grain overheating, a gluten break-down, a mold growth, the grain decay and infestation, odors arising and intensified ferments activity causing the grain quality loss. To eliminate these hazards, the recently used storage bins are applying processes such as cooling, ventilation or grain stirring more and more often.

7

Electromagnetic Stirring with Superimposed Travelling and Rotating Magnetic Fields

Cramer A., Pal J., Gerbeth G.

Przegląd Elektrotechniczny

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2008

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R. 84, nr 11

144-148

EN

Flow visualization and velocity measurements in a liquid metal flow were performed in order to study the combined action of a rotating and a travelling magnetic field. The combination of both fields, which is not necessarily a linear superposition, may give rise to an inherent three-dimensional constituent of the electromagnetic force distribution. As the Lorentz force may also become time-dependent, a quite intense mixing of metallic melts is achievable.

PL

Wizualizacja przepływu i pomiary prędkości przepływu ciekłego metalu zostały przeprowadzone celem przestudiowania łącznego działania wirującego i biegnącego pola magnetycznego. Kombinacja obu pól, która niekonieczne jest superpozycja liniową może spowodować, że rozkład sił elektromagnetycznych staje się trójwymiarowy. Skoro siła Lorenza może być także zależna od czasu można spodziewać się całkiem intensywnego mieszania kąpieli metalowej trójwymiarowe.

8

Aluminium composites casting in rotating magnetic field

Cholewa M., Dulęba A., Stawarz M., Formanek B.

Archives of Foundry Engineering

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2008

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Vol. 8, iss. 1

155-162

EN

In this paper technological and material conception of composite manufacturing with intensify of ex-situ powders and some results was shown. Technology of powders stirring with liquid metal in the crucible was shown. For composites required dispersion of reinforcement and matrix crystallization was assisted with rotating electromagnetic field. Improvement of reinforcing particles distribution can be observed. Composite structure was studied with use of light microscopy. Electromagnetic field processing positive influence on reinforcing phase distribution and matrix crystallization process was proved.