The aim of this work was to investigate the influence of distilled water flowrate in two different porousmembrane modules on the size of generated nitrogen nanobubbles. Modules had different diameter and number of membrane tubes inside the module. As bubbles are cut off from the membrane surface by a shear stress induced by the liquid flow, the change in the linear liquid velocity should result in a change of the generated bubble diameter. For both modules, higher flowrate of liquid induced generation of smaller bubbles, which was consistent with our expectations. This effect can help us in generation of bubbles of desired size.
This paper presents the results of experimental drum granulation of silica flour with the use of wetting liquids with different values of surface tension. Additionally, different liquid jet breakup and different residual moisture of the bed were applied in the tests. The process was conducted periodically in two stages: wetting and proper granulation, during which no liquid was supplied to the bed. The condition of the granulated material after the period of wetting (particle size distribution and moisture of separate fractions) and a change in the particle size distribution during the further conduct of the process (granulation kinetics) were determined.
The temperature dependence of the particle size distribution (PSD) of the magnetic fluid with an additional biocompatible dextran layer was studied using a ultrasonic method. The measurements of the ultrasound velocity and attenuation were carried out as a function of the volume concentration of magnetite particles at temperatures ranging from 15°C to 40°C. In order to extract the PSD from ultrasonic measurements, the theoretical model of Vinogradov-Isakovich was used. The extraction of PSD from the ultrasonic data requires also the measurements the density and viscosity of the ferrofluid samples. The calculated PSD of the magnetic fluid with an additional biocompatible layer shows a greater thermal stability than that of a magnetic fluid with a single surfactant layer.
The paper presents validation tests for method which is used for the evaluation of the statistical distribution parameters for 3D particles’ diameters. The tested method, as source data, uses chord sets which are registered from a random cutting plane placed inside a sample space. In the sample space, there were individually generated three sets containing 3D virtual spheres. Each set had different Cumulative Distribution Function (CDF3) of the sphere diameters, namely: constant radius, normal distribution and bimodal distribution as a superposition of two normal distributions. It has been shown that having only a chord set it is possible, by using the tested method, to calculate the mean value of the outer sphere areas. For the sets of data, a chord method generates quite large errors for around 10% of the smallest nodules in the analysed population. With the increase of the nodule radii, the estimation errors decrease. The tested method may be applied to foundry issues e.g. for the estimation of gas pore sizes in castings or for the estimation of nodule graphite sizes in ductile cast iron.
In technology of coal fines beneficiation in Poland mainly fines jigging processes are in use. In case of steam coal fines beneficiation it is till 80% of the whole amount of produced assortments, while in case of coking coal fines it is 100%. The necessary condition of not homogenous feed separation which is directed to beneficiation process in pulsating water stream is a sufficient liberation of particles. The stratification of particles in working bed causes that particles of certain size, density and shape gather in individual layers in working bed of jig. The introduction of sufficient amount of additional water determines appropriate liberation of particles group, which generates partition into concentrate and tailings. The paper presents the results of sampling of industrial jig used for the beneficiation of coal fines by three various settings of additional amount of water under sieve which is directed to jigging. These amounts were equal to 35, 50 and 70 [m3/h]. Collected samples of separation products were then sieved into narrow particle size fractions and divided into density fractions. In such narrow size-density fractions the coordinates of partition curves were calculated for tailings of hard coal fines, which were subsequently approximated by means of Weibull distribution function. The separation precision measured by separation density, probable error and imperfection were determined on the basis of obtained model separation curves. The evaluation of separation effects was performed for a wide particle size fraction: feed directed to jigging process and narrow particle size fractions. The analysis of separation results in size-density fractions allowed to determine the influence of particle size change on the value of probable error. The results of separation precision in size-density fractions were compared with effects of separation of wide particle fraction, i.e. feed directed to jigging process.
The purpose of the studies was to estimate efficiency of delivering nebulised drugs into the lower respiratory tract through endotracheal tubes (ET tubes) which are commonly used in the treatment of uncooperative patients. Water solution of Disodium Cromoglycate (DSCG) was nebulised with a constant air flow (25 l/min). Experimental studies were done for eight ET tubes with varying sizes (internal diameter, length) and made of two different materials. Size distribution of aerosol leaving ET tubes was determined with the use of aerosol spectrometer. Fine Particle Fraction (FPF) and Mass Median Aerodynamic Diameter (MMAD) were calculated for the aerosol leaving each tube. Additionally, mass of the Disodium Cromoglycate deposited into each endotracheal tube was determined. ET tubes can significantly influence the parameters of delivered aerosol depending on their diameter. FPF of aerosol delivered in to the respiratory tract is lower if small endotracheal tubes are used. However, MMAD and FPF for large endotracheal tubes are almost identical with MMAD and FPF from nebuliser. The results indicate that a substantial fraction of large droplets is eliminated from the aerosol stream in long endotracheal tubes (270 mm). In this case the mass of drug delivered through ET tubes is reduced but the content of small droplets increases (high value of FPF).
Acoustic radiation sources are successfully applied to cleaning rooms from dust of fairly large particle sizes (ten micrometers and larger). The sedimentation of fine aerosols (particle diameter of 1-10 microns) is a more complicated challenge. The paper is devoted to the substantiation of the acoustic sedimentation method for such aerosols. On the basis of the mathematical model analysis for aerosol sedimentation by the acoustic field the mechanisms of this process have been determined and include the particle coagulation acceleration and radiation pressure effect. The experimental results of the acoustic sedimentation of a model aerosol (NaCl) are shown. The calculation results according to the mathematical model for coagulation and sedimentation, on the basis of the Smolukhovsky’s equation taking into account various mechanisms of aerosol sedimentation by sound depending on the particle sizes and sound intensity, are given. The necessity to use intensive sources of high-frequency sound has been confirmed, suggesting that these sources must be located above dust clouds.
The main topic of this study is the experimental measurement and mathematical modelling of global gas hold-up and bubble size distribution in an aerated stirred vessel using the population balance method. The air-water system consisted of a mixing tank of diameter T = 0.29 m, which was equipped with a six-bladed Rushton turbine. Calculations were performed with CFD software CFX 14.5. Turbulent quantities were predicted using the standard k-ε turbulence model. Coalescence and breakup of bubbles were modelled using the homogeneous MUSIG method with 24 bubble size groups. To achieve a better prediction of the turbulent quantities, simulations were performed with much finer meshes than those that have been adopted so far for bubble size distribution modelling. Several different drag coefficient correlations were implemented in the solver, and their influence on the results was studied. Turbulent drag correction to reduce the bubble slip velocity proved to be essential to achieve agreement of the simulated gas distribution with experiments. To model the disintegration of bubbles, the widely adopted breakup model by Luo & Svendsen was used. However, its applicability was questioned.
The determination of the form of a probability density function (PDF3) of diameters for nodular particles by using a probability density function (PDF2), which form is empirically estimated from cross-sections of these nodules in a metallographic specimen, can be regarded as a special case of Wicksell's corpuscle problem (WCP). The estimation of the PDF3 for the nodular particles provides information about the kinetics of these particles nucleation, and so about the kinetics of their growth. This information is essential for building more accurate mathematical models of the alloy crystallization. In the paper there are presented two derivations of the methods used for the estimation of the PDF3 form. The first method bases on diameters received from a planar cross-section. The second one uses also data from the planar cross-section but not the diameters only chords. Both methods provide practical rules for the analysis of the empirical diameters’ and chord’s size distribution and allow to estimate the mean value of the external surface area of the particles.
This paper presents an effect of general dimensions of a reverse flow mini-cyclone with a tangential inlet on its separation efficiency. Several mini-cyclone design modifications are presented and evaluated for use in the air filtration systems of motor vehicles. Local design improvements of three components of a reverse flow mini-cyclone with a tangential inlet D-40 of an air filter fitted in an all-terrain vehicle engine were introduced. An asymmetric curvilinear shape of an outlet port was used instead of a symmetrical shape. An outlet vortex finder inlet port shape was streamlined, and a cylindrical outlet vortex finder of the cyclone was replaced with a conical one. Experimental evaluation of the effects of the design improvements of mini-cyclone on its separation efficiency and performance as well as flow resistance was carried out. Separation efficiency of the cyclone was determined using the mass method as a product of dust mass retained by the mini-cyclone and supplied to the mini-cyclone in a specified time. Separation performance of the cyclone was determined as the largest dust particle dz =dzmax in a specific test cycle in the cyclone outlet air stream. A polydisperse PTC-D test dust used in Poland, a substitute for AC-fine test dust was used. Dust concentration at the mini-cyclone inlet was kept at 1 g/m3. The size and total number of dust particles in the air stream at the outlet of the original mini-cyclone and at the outlet of the improved mini-cyclone was determined using a particle counter.
Decisions involving comparisons of Arabic number digits often exhibit an interference between the physical size of the digit and the implied numerical magnitude, a phenomenon called the size-congruity effect. Related research over the past four decades has yielded two competing models of the phenomenon: an early interaction account, where interference between numerical and physical magnitude occurs at an early encoding stage, and a late interaction account, where the interference occurs downstream as response competition during the decision process. In the present study, we asked participants to compare the physical sizes of pairs of Arabic digits. We fit the resulting response time distributions with a shifted Wald model, a single boundary accumulator model, which gave us estimates of information accumulation rate (drift rate), response threshold, and nondecision time. We found that incongruity between physical size and numerical magnitude affected the decision-related estimates of drift rate and response threshold. Further, a Bayesian analysis confirmed a null effect of congruity on nondecision time. These results indicate that the observed interference originates from decision-related processes, lending further support for a late interaction account of the size-congruity effect.
During a midwinter cruise north of 80oN to Rijpfjorden, Svalbard, the composition and vertical distribution of the zooplankton community were studied using two different samplers 1) a vertically hauled multiple plankton sampler (MPS; mouth area 0.25 m2, mesh size 200 μm) and 2) a horizontally towed Methot Isaacs Kidd trawl (MIK; mouth area 3.14 m2, mesh size 1500 μm). Our results revealed substantially higher species diversity (49 taxa) than if a single sampler (MPS: 38 taxa, MIK: 28) had been used. The youngest stage present (CIII) of Calanus spp. (including C. finmarchicus and C. glacialis) was sampled exclusively by the MPS, and the frequency of CIV copepodites in MPS was double that than in MIK samples. In contrast, catches of the CV-CVI copepodites of Calanus spp. were substantially higher in the MIK samples (3-fold and 5-fold higher for adult males and females, respectively). The MIK sampling clearly showed that the highest abundances of all three Thysanoessa spp. were in the upper layers, although there was a tendency for the larger-sized euphausiids to occur deeper. Consistent patterns for the vertical distributions of the large zooplankters (e.g. ctenophores, euphausiids) collected by the MPS and MIK samplers provided more complete data on their abundances and sizes than obtained by the single net. Possible mechanisms contributing to the observed patterns of distribution, e.g. high abundances of both Calanus spp. and their predators (ctenophores and chaetognaths) in the upper water layers during midwinter are discussed.
The aim of the study is to describe aspects of the life history of the Atlantic poacher (Leptagonus decagonus) obtained during early October 2010 and late September 2011 from the Hinlopen Strait, located between Nordaustlandet and the Spitsbergen Archipelago. Length was measured for 142 individuals, and 82 out of these were weighed, sexed and the age in years determined. The sex distribution in the population was 45% females and 55% males. Gut content examination revealed the domination of the mesopelagic and hyper−benthic calanoid Bradyidius similis that was recorded in 87% of the stomachs analysed. Overall there was a significant difference in size (length and weight) between the sexes, and a difference in length and weight at age between the sexes. There was no difference in age distribution between the sexes, but there was a larger age range within the male population than in the female population. The sexual dimorphism in size is likely linked to different reproductive strategies. This study represents the first data on the life history of the Atlantic poacher in Svalbard waters.
Feasibility of a model of gas bubble break-up and coalescence in an air-lift column enabling determination of bubble size distributions in a mixer with a self-aspirating impeller has been attempted in this paper. According to velocity measurements made by the PIV method with a self-aspirating impeller and Smagorinski’s model, the spatial distribution of turbulent energy dissipation rate close to the impeller was determined. This allowed to positively verify the dependence of gas bubble velocity used in the model, in relation to turbulent energy dissipation rate. Furthermore, the range of the eddy sizes capable of breaking up the gas bubbles was determined. The verified model was found to be greatly useful, but because of the simplifying assumptions some discrepancies of experimental and model results were observed.
The work presents results of solution combustion method utilization for yttria (Y2O3) nanopowder fabrication. Experiments were carried out with four different reducing agents: urea, glycine, citric acid and malonic acid added in stoichiometric ratio. The reactions were investigated using simultaneous DSC/DTA thermal analysis. After synthesis the reaction products were calcined at temperature range of 800-1100°C and analyzed in terms of particle size, specific surface area and morphology. Best results were obtained for nanoyttria powder produced from glycine. After calcination at temperature of 1100°C the powder exhibits in a form of nanometric, globular particles of diameter <100 nm, according to SEM analysis. The dBET for thus obtained powder is 104 nm, however the powder is agglomerated as the particle size measured by dynamic light scattering analysis is 1190 nm (dV50).
The objective of this investigation was comparing the penetration of chloride ions in ordinary and air-entrained concretes containing a waste material Fluidized Bed Combustion Fly Ash (FBCFA). All concretes were tested with 15% and 30% cement replacement by FBCFA, with the same water-binder ratio of 0.45. Two kinds of fly ash coming from fluid bed combustion in two power plants in Poland have been used. In this study the rapid chloride permeability test – Nordtest Method BUILD 492 method – was used. The microstructure of the concrete was analyzed on thin polished sections and the measurement of air voids sizes and their distribution, using digital image analysis, was carried on according to PN-EN 480-11:2008. Obtained results have shown a significant influence of partial cement replacement by FBCFA on the chloride ions movements in concrete. It has been found that this kind of addition reduced considerably the chloride ion penetration. The influence of air entrainment on the chloride diffusion coefficients was also measured and it was shown that application of air-entraining admixture for concretes with FBCFA reduce the chloride diffusion coefficient but it should be used with caution.
The analysis of particle size in suspensions carried out with use of the laser diffraction method enables us to obtain not only information about the size of particles, but also about their properties, shape and spatial structure, determined basing on fractal dimension. The fractal dimension permits the evaluation of the interior of aggregates, at the same time showing the degree of complexity of the matter. In literature, much attention is paid to the evaluation of the fractal dimension of flocs in activated sludge, in the aspect of control of single processes, i.e. sedimentation, dehydration, coagulation or flocculation. However, results of research concerning the size of particles and the structure of suspensions existing in raw and treated sewage are still lacking. The study presents optical fractal dimensions D3 and particle size distributions measured with use of laser granulometer in raw and treated sewage and activated sludge collected from six mechanical-biological wastewater treatment plants located in the Lower Silesian region. The obtained test results demonstrate that wastewater treatment plants that use both sequencing batch reactors and continuous flow reactors are more efficient at capturing suspension particles of a size up to 30 μm and are characterized by an increased removal of particles of a size ranging from 30 μm to 550 μm to the outflow. Additionally, in the case of samples of treated sewage and activated sludge collected at the same location, at short intervals, similar particle distributions were observed. As far as the analysis of fractal dimensions is concerned, particles contained in the raw sewage suspension were characterized by the lowest values of the fractal dimension (median equals 1.89), while the highest values occurred in particles of activated sludge (median equals 2.18). This proves that the spatial structure of suspension particles contained in raw sewage was similar to a linear structure, with a large amount of open spaces, while the structure of particles contained in the activated sludge suspension was significantly more complex in the spatial aspect.
Inexpensive synthesis of electroceramic materials is required for efficient energy storage. Here the design of a scalable process, flame spray pyrolysis (FSP), for synthesis of size-controlled nanomaterials is investigated focusing on understanding the role of air entrainment (AE) during their aerosol synthesis with emphasis on battery materials. The AE into the enclosed FSP reactor is analysed quantitatively by computational fluid dynamics (CFD) and calculated temperatures are verified by Fourier transform infrared spectroscopy (FTIR). Various Li4Ti5O12 (LTO) particle compositions are made and characterized by N2 adsorption, electron microscopy and X-ray diffraction while the electrochemical performance of LTO is tested at various charging rates. Increasing AE decreases recirculation in the enclosing tube leading to lower reactor temperatures and particle concentrations by air dilution as well as shorter and narrower residence time distributions. As a result, particle growth by coagulation - coalescence decreases leading to smaller primary particles that are mostly pure LTO exhibiting high C-rate performance with more than 120 mAh/g galvanostatic specific charge at 40C, outperforming commercial LTO. The effect of AE on FSP-made particle characteristics is demonstrated also in combustion synthesis of LiFePO4 and ZrO2.