Different Kinds Of Particles Research Articles

Simulation of Bubble Motion under Gravity by Lattice Boltzmann Method.

We describe the numerical simulation results of bubble motion under gravity by the lattice Boltzmann method(LBM), which assumes that a fluid consists of mesoscopic fluid particles repeating collision and translation and a multiphase interface is reproduced in a self-organizing way by repulsive interaction between different kinds of particles. The purposes in this study are to examine the applicability of LBM to the numerical analysis of bubble motions, and to develop a three-dimensional version of the binary fluid model that introduces a free energy function. We included the buoyancy terms due to the density difference in the lattice Boltzmann equations, and simulated single- and two-bubble motions, setting flow conditions according to the Eötvös and Morton numbers. The two-dimensional results by LBM agree with those by the Volume of Fluid method based on the Navier-Stokes equations. The three-dimensional model possesses the surface tension satisfying the Laplace's law, and reproduces the motion of single bubble and the two- bubble interaction of their approach and coalescence in circular tube. These results prove that the buoyancy terms and the 3D model proposed here are suitable, and that LBM is useful for the numerical analysis of bubble motion under gravity.

Linear stability of one-dimensional fluidized bed containing two kinds of solid particles

The behavior of a one-dimensional fluidized bed containing two kinds of solid particles is analyzed based on a three-fluid model with equations for the fluid phase: particle phase 1 and particle phase 2. Interactions among same kind of particles are assumed to be represented by both effective diffusion force and effective viscous force, and that between different kinds of particles by a force proportional to the relative velocity between them. Linear stabilities of this system are examined based on these models for various combinations of volume fractions of both particle phases. It is clarified that the present system in some cases is less unstable than a fluidized bed with one kind of particle.

Hydrodynamic dependence on riser diameter for different particles in circulating fluidized beds

With two different kinds of particles and three different circulating fluidized (CFB) bed risers, the riser diameter influences on bed density for different particles were investigated by measuring the total pressure drop across the whole riser and the axial profile of apparent voidage. The risers had the same bed height of 3.0 m but different inner diameters of 66, 97 and 150 mm, respectively. Particles of FCC and silica sand were used, which belong to types A and B of Geldart classification, respectively. It was found that riser diameter has opposite influences for Geldart A and B particles on the total pressure drop across the whole riser and the differential pressure gradient (apparent solids concentration) at a specified bed elevation. With increasing riser diameter, these two pressure drops increase for group B but decrease for group A particles, consistent with several other literature measurements in pilot-scale risers. As a result of these different dependencies of bed density on riser diameter, the saturation-carrying capacity, i.e., the solids circulation rate at the dilute suspension collapse, was also found to vary differently with riser diameter for different particles. That is, the increase in riser diameter increases the saturation-carrying capacity for Geldart A but decreases it for Geldart B particles.

Microfacies analysis and endogenic decay causes of carbonate building stones at the Asklepieion Epidaurus monuments of Peloponnessos, Greece

The carbonate building stones from the Asklepeion, Epidaurus, used to construct the monuments of Gymnasium, Tholos and Avaton can be grouped into 12 microfacies types, according to their microfacies characteristics such as the type of groundmass, the different kinds of particles, the facies-diagnostic fossils, the depositional and solution textures. Two of them, oocalcarenite (MF type I) and biocalcarenite (MF type II) belong to the marine Plio-Pleistocene carbonate sediments from Korinthos (ancient quarries in Kechries) and the northern part of the island of Aegina, respectively. Most of them, calcrete (MF type III), red biomicrites (MF type IV and V), oolitic grainstone (MF type VI), bio-grainstone (MF type VII), boundstone (MF type VIII), intrabreccia limestone (MF type IX), cherty biomicrite (MF type X) belong to the sedimentary carbonate formations of Mesozoic age of the adjacent areas in Argolis peninsula. The black lime-biomicrite (MF type XI) comes from a more distant sedimentary lithological formation, most probably from Dervenakia area (Tripolis zone). Finally, one belongs to the metamorphic carbonates (marbles of Naxos?). The endogenic decay causes are controlled by both sedimentary and diagenetic processes reflected in the microfacies type. So, the main endogenic factors of the oocalcarenite and biocalcarenite facies, which were used for the upper architectural members, are high porosity and the quantitative–qualitative mineralogical composition of the insoluble residue, which is mainly composed of swelling clay minerals (smectites). The calcrete facies, which was used in the foundations of all monuments, shows the heaviest decay problems which are related to the high structural irregularities, the high porosity and the quantitative–qualitative mineralogical composition of the non-carbonate minerals. The other facies appear with a weaker degree of decay whose endogenic causes are also investigated.

Experimental and theoretical studies of ultra-fine particle behavior in electrostatic precipitators

A cylindrical electrostatic precipitator (ESP) was used to investigate the applied voltage versus corona current characteristics and ultra-fine particle (diameter <0.1 μm) capture under controlled conditions. Corona currents were measured under various applied voltages for a one- and two-stage mode of operation. The corona current was observed to decrease at the higher gas velocities because fewer ions reached the collector surface. The presence of the particles (NaCl and Al 2O 3) in the ESP resulted in a decrease in the corona current due to a reduction in ion emissions. Collection efficiencies were measured under various operating conditions and it was found that lower electrical resistivity of particles resulted in the decrease of collection efficiency because of reduced attractive force at collector surfaces after deposition. A decrease in collection efficiency was observed (both in a one- and two-stage ESP for different kinds of particles, NaCl, Al 2O 3, and SiO 2) with the reduction in particle size below 0.1 μm. A statistical approach for particle-charging process, which assigns discrete charge levels to particles with the same size, in conjunction with the transport equation was used to support the experimental observations. This approach of fractional charging was more accurate than an assumption of uniform particle charging.

Characterization of Micelles of Polyisobutylene-block-poly(methacrylic acid) in Aqueous Medium

Four amphiphilic block copolymers polyisobutylene-block-poly(methacrylic acid) (IBm-MAAn; m = 70−134, n = 52−228) were synthesized and transferred into aqueous medium at pH 10−12. Their structure in solution was characterized by fluorescence correlation spectroscopy (FCS), static and dynamic light scattering (SLS, DLS), analytical ultracentrifuge (AUC), and by transmission electron microscopy (TEM) with freeze-fracturing and staining techniques. DLS data, AUC sedimentation traces, and TEM images indicate at least two different kinds of particles. TEM shows spherical micelles; however, especially for polymers with larger hydrophobic blocks, additional particles are observed. FCS shows extremely low critical micelle concentrations (cmc < 0.3 mg/L). The main part of the particles consists of micelles with diameters from 15 to 50 nm, built by 130−200 block copolymer molecules. Aggregation numbers and diameters are consistent with a model recently proposed by Förster et al. (J. Chem. Phys. 1996, 104, 9956−9970). The packing densities are determined from the hydrodynamic diameters and the aggregation numbers; they vary between 6 and 32%. For large hydrophobic block lengths additional structures are found, in most cases with a narrow size distribution. The origin of these structures is discussed.

Liquid-Solid Separation of Photo-Catalyst Suspension Induced by Ultrasound

A method for the induction of the agglomeration of different kinds of particles by the ultrasonic irradiation in the water was studied. This method has been proven to be applicable to the separation of photo-catalyst particles from the drainage of photo-oxidation process. The catalyst particle was titanium oxide with the average diameter of 3 µm. The agglomeration was observed when the ultrasound with the frequency of 26 kHz and the power of 80 W was irradiated and a certain amount of glass beads with the diameter between 33-44 µm were added. The catalyst particles deposited on the glass beads, and then settled together with the glass beads leading to the liquid-solid separation. It was also found that the addition of the glass beads has also enhanced the agglomeration among the catalyst particles themselves.

Surface Force Field as a Factor Promoting the Dissociation of X2 Molecules

The dissociation of X2 molecules in the surface layer of a condensed phase is governed by the surface-force energy, which is positive and arises from the interaction of particles of different kinds.

Assembling of Mono-Sized Particles for the Percolation Control of Composition Graded Multi-Phase Packing Arrangements

A particle assembling apparatus was devised, in which individual single particles are positioned at the allotted sites on an ordered lattice according to a given configuration pattem. The apparatus consists of particle conveying arm with a suction tip for holding a single particle, three stock pallets for three kinds of particles, and a configuration pallet. The software that drives mechanical motions of the conveying arm and the suction tip was so designed that the movement of the individual parts follows without delay to the electronic signal guided by the computer program. The particles stocked in the stock pallets are picked up one by one with a suction tip and conveyed to the configuration pallet to be laid on the pre-designed sites. The arranged two dimensional particle array is then stacked layer by layer in a packing bucket to form a three dimensional cubical arrangement. Three stock pallets for three different kinds of particles, and ten thousands of configuration sites are available. One arrangement cycle needs several seconds, depending on the manipulating speed of the mechanical parts. Packing arrangements of three kinds of balls with a diameter of I mm were well fabricated by the present apparatus, and various types of percolation and graded structures have been realized.

Continuous Monitoring and Mechanism of Electrostatic Charge of Powder in Fluidized Bed Process.

In a previous paper (Watano et al., J. Soc. Powder Technol. Jpn, 34, 778, 1997), we developed a novel system which could continuousy monitor the electrostatic field strength of powder in a fluidized bed process. This paper reports further study related to the electrostatic characteristics of powder. Two novel achievements are described; one is an improvement of the reliability and accuracy of the sensor, and the other is the mechanism and characteristics of the electrostatic charge for different kinds of powder materials. First, the structure of the sensor extremity has been improved to remove the troubles encountered in the previous sensor. By using a double-walled cylinder, the sensor is devised to tolerate severe vibration, high purge air flow and particle sticking. By increasing the sensitivity, the accuracy of measurement can be increased by approximately five times that of the previous sensor. Secondly, the relationship between electrostatic field strength and the electrical charge of the particles has been investigated using various kinds of powder materials. The sensor shows a good linearlty between two measurements, proving that the electrostatic characteristics of charged particles could be monitored correctly via the electrostatic field strength. The performance of the system has been confirmed in the fluidized bed granulation/drying processes using different kinds of particles. The mechanism of the electrostatic charge for different kinds of powdered materials are also discussed.

Thermal power at a substrate during ZnO:Al thin film deposition in a planar magnetron sputtering system

In a balanced magnetron sputtering system the thermal power at a substrate has been determined from the temperature change of the substrate when the plasma is switched on. Using the temperature as a function of the potential of a probe, the calorimeter has been calibrated absolutely. A heat input equivalent of about 10 eV per electron has been determined for a dc discharge. The results for the total thermal power at the substrate are compared with values published by other groups for similar discharge systems. The contributions of different kinds of particles are discussed. For the dc discharge at a discharge power of 50 W and a pressure of 0.8 Pa, a thermal power of 15.6 mW cm−2 has been found which is mainly produced by particles other than the plasma ions. It can be concluded from the increase of the thermal power with decreasing pressure that bombardment by particles originating from the target is the main source of the substrate heating. In an rf discharge the ion energy is two times and the flux density is nearly three times higher than in a dc discharge. Here the dependence of the thermal power on pressure is only weak and mainly the plasma ions transport the power to the substrate.

The effect of interfacial adhesion on toughening behaviour of rubber modified poly(methyl methacrylate)

In order to study the effect of interfacial adhesion and particle size on the toughening behaviour of rubber-toughened poly(methyl methacrylate) (PMMA), a systematic model study has been carried out using two different kinds of particles, i.e. ‘core’ and ‘core—shell’ type particles. The core particle consists of poly( n-butyl acrylate) (PBA), while the core—shell particle has a PBA core and a PMMA outer shell. The prepared particles were blended with matrix PMMA. The values of fracture toughness, K IC, determined by three-point-bending tests at a relatively low strain rate and room temperature, did not show any difference for core blends and core—shell blends. However, the value of K IC at a high strain rate and relatively low temperature and impact strength showed a marked difference between core blends and core—shell blends. These results imply that even though there is no primary chemical bonding between PBA particles and the PMMA matrix for core blends, the interfacial adhesion strength is strong enough to induce matrix deformation at relatively low strain rate, which resulted in similar fracture toughness for both of the blends. However, at a relatively high strain rate, the interfacial failure occurs predominantly, which would not induce much of the matrix PMMA deformation, so the core blends show relatively low fracture toughness.

Removal of different kinds of particles in deep bed filters consisting of permeable synthetic collectors (PSC)

The possible use of deep bed filter media composed of permeable synthetic collectors (PSC's) was studied. The PSC's were made of open porous plastic foam or non-woven fabrics in the shape of cylinders with dimensions of some millimeter. With such media, particle retention takes place throughout the entire body of the collectors. Theoretical analysis based on trajectory calculations for non-Brownian particles was carried out for estimating the particle collection efficiency. A parametric study was made to examine the effect of various operating variables (e.g. inner porosity and fibre diameter of the PSC's) and of particle characteristics (e.g. their size and density). In contrast to conventional deep bed filtration using impermeable filter grains, filtration using PSC's performs much better in particle collection. This conclusion was confirmed by experiments with different kinds of particles for the initial and dynamic phase of filtration. Special investigations using an endoscope showed that the adhesion behaviour of the particles inside the PSC's is getting more and more important with increasing amount of deposited particles in the collectors.

Removal of different kinds of particles in deep bed filters consisting of permeable synthetic collectors (PSC)

The possible use of deep bed filter media composed of permeable synthetic collectors (PSC's) was studied. The PSC's were made of open porous plastic foam or non-woven fabrics in the shape of cylinders with dimensions of some millimeter. With such media, particle retention takes place throughout the entire body of the collectors. Theoretical analysis based on trajectory calculations for non-Brownian particles was carried out for estimating the particle collection efficiency. A parametric study was made to examine the effect of various operating variables (e. g. inner porosity and fibre diameter of the PSC's) and of particle characteristics (e. g. their size and density). In contrast to conventional deep bed filtration using impermeable filter grains, filtration using PSC's performs much better in particle collection. This conclusion was confirmed by experiments with different kinds of particles for the initial and dynamic phase of filtration. Special investigations using an endoscope showed that the adhesion behaviour of the particles inside the PSC's is getting more and more important with increasing amount of deposited particles in the collectors.

Different fates of phagocytosed particles after delivery into macrophage lysosomes.

Phagocytosis in macrophages is often studied using inert polymer microspheres. An implicit assumption in these studies is that such particles contain little or no specific information in their structure that affects their intracellular fate. We tested that assumption by examining macrophage phagosomes containing different kinds of particles and found that although all particles progressed directly to lysosomes, their subsequent fates varied. Within 15 min of phagocytosis, >90% of phagosomes containing opsonized sheep erythrocytes, poly-e-caprolactone microspheres, polystyrene microspheres (PS), or polyethylene glycol-conjugated PS merged with the lysosomal compartment. After that point, however, the characteristics of phagolysosomes changed in several ways that indicated differing degrees of continued interaction with the lysosomal compartment. Sheep erythrocyte phagolysosomes merged together and degraded their contents quickly, poly-e-caprolactone phagolysosomes showed intermediate levels of interaction, and PS phagolysosomes became isolated within the cytoplasm. PS were relatively inaccessible to an endocytic tracer, Texas red dextran, added after phagocytosis. Moreover, immunofluorescent staining for the lysosomal protease cathepsin L decreased in PS phagolysosomes to 23% by 4 h after phagocytosis, indicating degradation of the enzyme without replacement. Finally, PS surface labeled with fluorescein-labeled albumin showed a markedly reduced rate of protein degradation in phagolysosomes, when compared to rates measured for proteins in or on other particles. Thus, particle chemistry affected both the degree of postlysosomal interactions with other organelles and, consequently, the intracellular half-life of particle-associated proteins. Such properties may affect the ability of particles to deliver macromolecules into the major histocompatibility complex class I and II antigen presentation pathways.

Experimental and theoretical determination of concentration profiles and influence of particle characteristics in blowing snow

Snow drift transport may cause avalanches on the roads during the periods of snowfall and strong wind. To better understand the factors influencing transport we have developed a theoretical model. This model is based on the boundary layer theory, where the particle mass conservation is considered. Assuming that the saturation is reached, the concentration profile can be represented by a negative exponential law. By means of this analysis, the influence of particle characteristics is explored through the roles of threshold friction velocity and fall velocity. Using fluid mechanics laws, an analysis of the concentration profile resulting from the effect of the wind on a particle bed was also developed. For several velocities of flow and for different kinds of particles an experimental determination of the concentration profile was achieved. We used a laser visualisation and image processing technique to carry out these experiments. The obtained results fit with the values predicted by the theoretical model.

Aufbereitung verschiedener Partikelarten aus Miscanthus sinensis zur Herstellung von Werkstoffen

Preparation of different kinds of particles and fibrous materials from Miscanthus sinensis for the production of materials.

ON COLOR QUANTIZATION: RELATIONS AND PARASTATISTICS

Particle operators for the description of a system of families of particles of different kind are introduced. The generalized commutators and Klein transformations are discussed in some detail. The color description of parastatistics is given.

Dynamic critical phenomena in aqueous protein solutions.

An aqueous protein solution is a binary mixture of large particles (protein molecules) and small particles (water molecules). In contrast, a binary liquid mixture is a mixture of two different kinds of particles that are approximately the same size. Thus, a comparison of the critical behavior in these two systems allows one to determine the effect on critical behavior of a relative difference of size in the two kinds of particles in a binary mixture. The correlation length j, osmotic compressibility kT , and coexistence curve of aqueous protein solutions in the vicinity of the critical point for liquid-liquid phase separation have been reported recently [1‐3]. These experimental results established that the static critical properties of these solutions are consistent with the behavior of members of the static universality class of three-dimensional systems with short range interactions and scalar order parameters. This universality class includes binary liquid mixtures. In contrast to the equilibrium properties, the dynamic properties of aqueous protein solutions in the vicinity of the critical point have not been investigated as thoroughly. In this Letter, we report our use of quasielastic light scattering (QLS) to investigate the time decay of spontaneous concentration fluctuations, as a function of both wave number q of the fluctuations and temperature T, along the critical isochore of aqueous solutions of the bovine eye lens protein gII-crystallin. The only previous study of critical dynamics in a protein solution of which we are aware is the work of Ishimoto and Tanaka who made QLS measurements at a single fixed wave number of the fluctuations using a 19 channel digital correlator on aqueous solutions of lysozyme [4] along the critical isochore for sT 2 TcdyTc $ 5 3 10 23 (q j, 0.1), where Tc is the critical temperature. The present study is a significant experimental advance over the work of Ishimoto and Tanaka in that (i) we obtain data for fluctuations at up to 12 different wave numbers, (ii) we obtain data using a 144 channel digital correlator, and (iii) we obtain data much closer to the critical point [ sT 2 TcdyTc $ 1.56 3 10 24 and q j# 3.18]. The more thorough investigation of critical dynamics presented here has revealed new and unexpected behavior. Specifically, we find that the wave number and temperature dependence of the average rate of decay of the concentration fluctuations are consistent with the theory for critical dynamics in binary liquid mixtures [5] only if we allow both the background viscosity and the background contribution to the decay rate to be unusually large. Furthermore, in contrast to the behavior seen in binary liquid mixtures we find that the concentration fluctuations exhibit very significant deviation from exponential decay with time. Of course, these protein solutions may be viewed as

Separation of mixed fine powders by electrophoresis

A sub-micron powder of either alumina or zirconia was separated by electrophoresis. A mixed suspension of these powders was prepared at a powder concentration of 150–200 p.p.m. at pH 5.0, where both alumina and zirconia had enough positive zeta potential to prevent their heterocoagulation. A uniform and stable ascending flow of electrolytic solution at pH 7.4 was prepared, where the difference of the zeta potential between alumina and zirconia was about the maximum. The ascending flow carried a fine stream of the suspension with a diameter less than 1 mm. The fine stream of suspension was divided into two fine streams by applying an electric field of 10 V/cm perpendicular to the flow. The concentration of different kinds of particles in each separated suspension was reduced to 1/10 of that in the original mixed suspension.