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Kravtsov, A. G.; Zotov, S. V.; Brünig, Harald

doi:10.1023/a:1006762701365

Cited by 8 publications

(5 citation statements)

References 3 publications

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“…The previously established [5,11] partial preservation of the electrical activity of electret fibres in liquids (up to 70% effective surface charge density for 1 month) was confirmed, which could be explained by the reversible character of the reaction of the electret charge with both the liquid and the disperse contaminants it contained. The characteristics of the combined effect of charge, magnetic field, and modifiers added to FE require further investigation using industrial equipment.…”

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confidence: 63%

Use of modified polymer fibre materials as filter elements for treatment of multiphase media

et al. 2009

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Fibre materials manufactured with modern, environmentally clean, solution-free, meltblown technology are convenient and economical polymer filters. The method of manufacturing fibre materials for such filters can be introduced in polymer processing plants interested in implementing progressive technology and expanding the line of polymer fibres and commercial articles manufactured from them.Filtration of multiphase media -liquids or gases -is the unavoidable companion of many modern manufacturing processes. With respect to structural organization, polymer fibre materials have long been considered optimum filtration systems, so that they are used in the most varied sectors [1][2][3]. A number of promising versions of fibre filter elements based on melt blowing technology -aerodynamic spinning of fibres from melts of large-tonnage manufactured polyolefinshas now been developed [4,5]. The developments in creating polymer fibre filters in Belarus are gradually approaching industrial introduction [6].Liquids and gases are filtered directly on porous fibre filters under the effect of many mutually interrelated factors; the fundamental ones are the flow rate of the filtered dispersion medium, the concentration of disperse particles of contaminants in it, the shape and size of pores and channels in the porous fibre filter, and the intensity of interactions in the "contaminant particle-filter membrane" system. The presence of electric or magnetic fields of determined strength in the system, whose simultaneous effect on the contaminant particles can significantly increase the filtration efficiency, is especially important. In industrial separators, the fields are usually regenerated with powerful voltage sources. However, some varieties of porous polymer fibre filter materials have electrical and/or magnetic activity, so that using them as feed for filtration systems is expedient and economically justified [1][2][3]. For this reason, the search for progressive methods of modifying polymer fibre materials becomes pressing. There are two groups of such methods -incorporating active additives in the fibres and treating the fibres in electric or magnetic fields. Many studies have shown that it is useful to combine several methods of treating the fibres [4,5,7].Electrical treatment of the spun hot melt-blown fibres in a corona discharge field of varying strength is usually used to give filter materials electrical activity, and filling the fibres with magnets (usually barium or strontium ferrites) followed by treatment in pulsed magnetic fields is used to impart magnetic activity [1]. At the same time, it has repeatedly been noted [5,7] that the electret and magnetic properties become interconnected in such fibres. For this reason, we can hypothesize that composite fibre materials can exhibit combined -adsorption, electrical and magnetic -activity with respect to filtered multiphase media in contact with them [8].We demonstrated the possibilities of some varieties of polymer fibre filter elements obtained with melt blowing techn...

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confidence: 63%

Use of modified polymer fibre materials as filter elements for treatment of multiphase media

et al. 2009

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“…The polypropylene fibers used in masks usually have a surface charge. Such fibers are called electrets and the surface charge arises due to the trapping of charge carriers at defects during the manufacturing process or it is applied on finished respirators, commonly with the corona-discharge method [35][36][37]. With the accumulation of particles on the surface of the thicker fibers the charge is screened and the PRE drops, especially for particles with smaller diameter, which can be seen on the PRE given as a particle diameter vs. time in Figures S9 and S10.…”

Section: Time-dependent Measurementsmentioning

confidence: 99%

Size- and Time-Dependent Particle Removal Efficiency of Face Masks and Improvised Respiratory Protection Equipment Used during the COVID-19 Pandemic

Krajnc

Pirker

Centa

et al. 2021

Sensors

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Size- and time-dependent particle removal efficiency (PRE) of different protective respiratory masks were determined using a standard aerosol powder with the size of particles in the range of an uncoated SARS-CoV-2 virus and small respiratory droplets. Number concentration of particles was measured by a scanning mobility particle sizer. Respiratory protective half-masks, surgical masks, and cotton washable masks were tested. The results show high filtration efficiency of FFP2, FFP3, and certified surgical masks for all sizes of tested particles, while protection efficiency of washable masks depends on their constituent fabrics. Measurements showed decreasing PRE of all masks over time due to transmission of nanoparticles through the mask-face interface. On the other hand, the PRE of the fabric is governed by deposition of the aerosols, consequently increasing the PRE.

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“…The standard (equal-time or -frequency) Wigner distribution (WD) is a quasi-probability density function in phase space and was first introduced by E. Wigner [9] in connection to quantum thermodynamics and later found wide-ranging applications in classical [10], [11], as well as in quantum optics [1], [12]. In classical optics, a main use of the Wigner distribution is connected to high-frequency asymptotic and radiative transfer, both of which can be most naturally worked out from the first principle in phase space (see the review [13], [14] and references therein).…”

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confidence: 99%

Space-frequency correlation of classical waves in disordered media: High-frequency and small-scale asymptotics

Fannjiang¹

2007

Europhys. Lett.

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Two-frequency radiative transfer (2f-RT) theory is developed for geometrical optics in random media. The space-frequency correlation is described by the two-frequency Wigner distribution (2f-WD) which satisfies a closed form equation, the two-frequency Wigner-Moyal equation. In the RT regime it is proved rigorously that 2f-WD satisfies a Fokker-Planck-like equation with complex-valued coefficients. By dimensional analysis 2f-RT equation yields the scaling behavior of three physical parameters: the spatial spread, the coherence length and the coherence bandwidth. The sub-transport-mean-free-path behavior is obtained in a closed form by analytically solving a paraxial 2f-RT equation.

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Cited by 8 publications

References 3 publications

Use of modified polymer fibre materials as filter elements for treatment of multiphase media

Use of modified polymer fibre materials as filter elements for treatment of multiphase media

Size- and Time-Dependent Particle Removal Efficiency of Face Masks and Improvised Respiratory Protection Equipment Used during the COVID-19 Pandemic

Space-frequency correlation of classical waves in disordered media: High-frequency and small-scale asymptotics

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