ASSESSMENT OF RED BLOOD CELL DEFORMABILITY BY CENTRIFUGAL SEDIMENTATION

A centrifugal sedimentation method (CSM) is proposed for the assessment of deformability of red blood cells. The method is based on the premise that a red blood cell (RBC) should deform in a centrifugal field due to the variation of the centrifugal acceleration with the distance from the center of rotation. This change in shape of the RBC leads to a change in the rate of sedimentation in the centrifugal field. The rate of sedimentation, which serves as a measure of deformability, is characterized by an apparent sedimentation coefficient (ASC) and its normalized value (NASC), which is calculated by comparison with a control group of normal RBCs. It has been shown that the NASC is sensitive to the speed of rotation, to treatments with glutaraldehyde, diamide, or chlorpromazine, to heat treatment and to osmotic pressure variations.     

Fundamental particle fluidization behavior and handling of nano-particles in a rotating fluidized bed

The fluidization behavior of the three kinds of nano-particles (TiO₂, SiO₂, Al₂O₃) was analyzed in a rotating fluidized bed (RFB). Bed pressure drop, minimum fluidization velocity, bed expansion, entrainment and particle mixing characteristics under various centrifugal accelerations were experimentally investigated. The effects of centrifugal acceleration on agglomerate size and density were analyzed based on a Richardson-Zaki approach coupled with a fractal model.The bed pressure drop behavior showed almost similar to that of A or B-particles of Geldart's classification. Dimensionless particle bed height became smaller when the centrifugal acceleration was larger. Size of agglomerate decreased and its density increased with an increase in centrifugal acceleration. The agglomerate size in the RFB showed smaller than that in other types of fluidized bed system such as vibration and magnetic field as well as in a conventional fluidized bed, and the agglomerate density became larger. Particle entrainment became smaller in the case of the higher centrifugal acceleration. These results confirmed that the RFB can reduce the size of a nano-particle agglomerate and fluidize nano-particles at high gas velocity without any significant entrainment. The RFB is thus expected as more effective gas-solid fluidization system for handling of a large amount of nano-particles than other types of fluidized bed.     

Bunker design based on experiments in a bunker-centrifuge

Experimental investigations of other authors have shown that there exists some uncertainty about the hopper design based on the Jenike method.Direct experiments on critical hopper outlet dimensions have been carried out with the aid of a bunker-centrifuge, where gravity acceleration has been replaced by centrifugal acceleration adjustable in the range up to 100 times the gravity acceleration. The advantage of this method is threefold: (1) direct experimental determination of the critical outlet dimensions without any assumptions; (2) only a small amount of solids needed by comparison with gravity flow experiments; (3) variations of centrifugal acceleration instead of different outlet sizes.     

Molding of conical ceramic articles from aqueous slurry

Results of design and construction developments focused on the problem of centering of a core in the cavity of a gypsum mold, the production of ceramic blanks with thickness variability and specified shape, and ways of increasing the uniformity of articles in molding of large sheathing for antenna radomes by means of aqueous slurry casting are presented.     

Study on Metals Recovery from –0.074 mm Printed Circuit Boards by Enhanced Gravity Separation

Nowadays study on discarded printed circuit boards (PCBs) reutilization has great significance for achieving secondary resources recycling and preventing environmental pollution. Physical methods show great potential and advantages on discarded PCBs reutilization, comparing with chemical and biological methods. However for the particles of -0.074 mm PCBs, little work has been done in the past because of lower separation efficiency and recovery. In this paper, the conundrum of -0.074 mm PCBs reutilization was resolved successfully with the help of Falcon concentrator. Separation mechanism for fine particles with different mass densities in a Falcon centrifugal concentrator was analyzed. The main factors such as magnitude of rotation frequency (centrifugal acceleration), anti-charge water pressure and feeding concentration were studied, and interaction of different factors was analyzed using Design-Expert software. The experimental results show that metals grade of -0.074 mm PCBs and integration efficiency were obtained as 76.89% and 80.77% respectively when feeding concentration was 40 g/L with water pressure of 0.01 MPa and rotation frequency of 50 Hz.     

Centering molding assemblies

Methods are surveyed for centering molding assemblies as used to mold large ceramic blanks from aqueous slip. Existing and promising future methods of centering are examined, with emphasis on their advantages and shortcomings. The analysis shows that video centering is the most promising method.     

高黏度聚乳酸(PLA)熔体微分离心静电纺丝

离心纺丝已成为制备超细纤维的有效途径,将离心纺丝和静电纺丝结合起来的离心静电纺丝,纺丝效率高、纤维细度低。但是目前离心静电纺丝相关的研究十分有限,且主要涉及溶液离心静电纺丝。为了解决这一问题,本文设计了一种基于熔体微分的熔体离心静电纺丝装置,选取聚乳酸（PLA）作为研究对象,探究了挤出机转速和流量的关系,得出挤出机转速在20r/min、流量为1.6089g/min时纺丝效果最佳。研究了离心盘转速、纺丝电压等因素对纤维的影响,得出增加离心盘转速可大幅细化纤维直径,离心盘转速提高1倍,纤维直径减小77.26%;纺丝电压的加入不仅可以细化纤维直径,而且可以提高纤维的结晶度。结果表明：熔体微分离心静电纺丝可以高效制备PLA超细纤维,并且通过改变实验参数可以控制纤维特征,为离心静电纺丝产业化提供实验依据。     

Prediction of fiber orientation in a rotating compressing and expanding mold

In the rotating/compressing/expanding mold (RCEM), one mold wall can expand, compress, and rotate during injection molding, thus offering opportunities to control the thermomechanical history of a polymer and its microstructure. A computer simulation of flow and fiber orientation in RCEM was developed. The predictive model extends the generalized Hele‐Shaw formulation to account for compression/expansion and rotation of the mold wall, and uses the Folgar–Tucker model for fiber orientation predictions. A 20% GF polypropylene was molded under various molding conditions. The predicted fiber orientation distributions were compared with experiments. The model compares favorably with experiments, provided that the fiber orientation equation is modified by a strain‐reduction factor that slows the transient development of fiber alignment. The effect of fountain flow on orientation must also be included to correctly predict fiber orientation near the mold walls, mainly for the case of stationary and linear motions of the mold surface. Compression or expansion of the mold has only a small effect on fiber orientation, but rotation of the mold dramatically changes the orientation, causing fibers to align in the tangential direction across the entire thickness of the molding. This rotation action perturbs the fountain flow and becomes the dominant factor affecting fiber alignment across the entire cavity thickness. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Chlorine evolution in a centrifugal field

Intensification of the electrochemical production of chlorine and sodium hydroxide (i.e., the chlor-alkali process) was demonstrated in a centrifugal acceleration field. This intensification was shown by comparing the cell voltages and the anode potentials for a cell operated with and without a centrifugal field applied using the linear sweep voltammetric, galvanostatic and potentiostatic polarizations. Under industrial chlor-alkali electrolysis conditions, a cell voltage reduction of up to 600 mV and an anode potential reduction of up to 360 mV at 600 mA cm^–2 were achieved by using a relative acceleration rate of 190 g with an acidic saturated NaCl solution at 80 °C. The relationships between the cell performance and relative acceleration rate, for different anode materials, temperature and NaCl concentration are reported.     

SHS in conditions of rotation: Thermal and concentration combustion limits for oxide systems taken as an example

Potential possibility of using centrifugal forces for production of noble ferroalloys was demonstrated for aluminothermic systems taken as an example. Combustibility limits in the field of centrifugal forces were associated with the onset of adiabatic conditions for combustion due to acceleration of combustion front by melted metal particles returned into the reaction zone by centrifugal forces.     

A Device for Countercurrent Distribution of Particles by an Aqueous Polymer Two-Phase System

Abstract

A new device for countercurrent distribution using an aqueous polymer two-phase system was developed. The device consists of a rotating column separated into many loculi in which steel balls are placed as stirrers, and a motor is used to rotate the column at two selected speeds alternately. At the lower speed of rotation with little centrifugal force, the steel balls roll down along the surface of column wall and promote effective mixing, while at the higher speed of rotation the centrifugal force keeps the balls still and accomplishes phase separation.

The distribution behavior of cells or cell particles by the device is demonstrated with red blood cells from rat.     

Centrifugal Filter for Aerosol Collection

Air filters collect particles by the mechanical collection mechanisms, namely, inertia, interception, gravitational settling, and Brownian diffusion. There exists the most penetrating particle size (MPPS) in submicron size range for which none of the collection mechanisms work effectively. In this study, we propose a new type of filter named as “centrifugal filter,” which collects aerosol particles by centrifugal force together with the conventional mechanical collection mechanisms. The centrifugal filter proposed in the present work may be rotated by a motor or compressed air. Air passes through the filter in the axial direction of filter rotation. The filter rotates so does the air embedded in the filter, and therefore centrifugal force exerts on particles. In addition to the mechanical collection mechanisms, small migration of particles due to the centrifugal force enhanced the collection efficiency of submicron particles significantly without increasing the pressure drop. The performance tests of centrifugal filter were conducted by changing the fiber diameter, the air flow velocity and the rotation speed. We found that the collection efficiency of filter is enhanced significantly by rotating the filter without increasing the pressure drop and that the filter efficiency is well predicted by the conventional filtration theory accounting for the centrifugal force.

Copyright 2015 American Association for Aerosol Research     

Application of centrifugal filter to aerosol size distribution measurement

In the present work, the centrifugal filter proposed by the authors was applied to classify aerosol particles followed by the detection of total mass or number concentrations so as to measure the size distribution of aerosol particles. The structure and operating condition of the centrifugal filter were optimized in order to attain sharp separation curves with various cut-off sizes between 0.3 and 10 μm. The aerosol penetrating the centrifugal filter at various rotation speeds was measured with a photometer to determine the total mass concentration. The virtue of this system is that the cut-off size is varied just by scanning the rotation speed of filter and that it can be applied to the measurement of high concentration aerosols without dilution by choosing an appropriate filter medium. As a result, the centrifugal filter was successfully applied to measure the size distribution of solid particles in size ranging from 0.3 to 10 μm.

Copyright © 2017 American Association for Aerosol Research     

Chemical inhomogeneity in commercial alumina powders and its effect on abnormal grain growth during sintering

Chemical inhomogeneity in four commercial alumina powders and its effect on the abnormal grain growth (AGG) during sintering have been investigated. Classification and chemical analyses revealed that relatively small portions of coarse particles in all the powders contained a significantly higher concentration of impurities than their corresponding large portions of fine particles. Hot pressing showed that AGG occurred for all the coarse portions whereas there was no significant indication of AGG for the fine portions. AGG also occurred for all unclassified powders during sintering at the interfaces of bilayer specimens fabricated by repeated centrifugal casting, which could also be attributed to the coarse particles mass-segregated during centrifugal casting. Results of this investigation indicate that coarse particles in commercial purity alumina powder generally contain high concentration of impurities and thus can cause AGG during sintering. Particle aggregates were attributed to the high concentration of impurities in the coarse portions.     

Effect of Process Parameters on Solute Centrifugal Extraction from Electropermeabilized Carrot Gratings

The solute aqueous centrifugal extraction from carrot gratings was investigated through the effect of some process parameters (centrifugal acceleration, solution temperature and liquid to solid ratio). The carrot gratings were treated by a pulsed electric field (PEF) (670 V cm⁻¹ and 300 pulses of 100 μs) and then subjected to an aqueous centrifugal extraction (accelerations from 14 × g to 5434 × g) at temperatures in the range 18–35°C. The effect of carrot tissue mild preheating (30–50°C) before PEF was also investigated.The increase of centrifugal acceleration up to 150 × g enhances extraction kinetics. The solute concentration then reaches 96% after 25 min of extraction at room temperature or after 15 min of extraction at 35°C. However, any further increase in centrifugal acceleration does not provide more acceleration of extraction. A tissue preheating at 50°C allowed an easier electrical permea-bilisation of cell membranes at lower PEF intensity (300 V cm⁻¹) and shorter PEF extent (30 pulses). A maximum solute yield is then obtained. The kinetics of centrifugal aqueous extraction was described by a single exponential model.     

Refining of Silicon Using an Induction Furnace in the Fractional Melting Process

A new fractional melting process using an induction furnace and a centrifugal system has been developed for metallurgical-grade silicon (MG-Si) refining. An induction furnace enables rapid heating and therefore reduces the total refining process time. Impurity-rich liquids can be ejected effectively from the MG-Si by the centrifugal force induced by a motor. The impurity behaviors of the refined samples are observed by scanning electron microscope (SEM). The refining efficiency, which depends on sample size and centrifugal force, is evaluated using inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectroscopy (ICP-MS). The purity of the refined silicon increases with the centrifugal force. The correlation between the centrifugal force and silicon purity is rationalized using the surface tension of impurity-rich liquids. In spite of the rapid heating rate by induction furnace, the MG-Si is refined and 96.7% of the impurities are removed at rotation speeds of 3000 rpm.     

Formation of compositional gradient in Al/SiC FGMs fabricated under huge centrifugal forces using solid-particle and mixed-powder methods

Formations of graded distribution of SiC ceramic particles within the hollow cylindrical shaped Al/SiC functionally graded materials (FGMs) fabricated by centrifugal solid-particle method (CSPM) and centrifugal mixed-powder method (CMPM) under huge centrifugal force are experimentally and theoretically investigated. The movement of SiC ceramic particles in viscous liquid under centrifugal force is explained based on Stoke's law. The effect of compositional gradient of particles on viscosity is taken into account. Also, the effect of temperature distribution on viscosity and density are considered. A computer code to simulate the formation of compositional gradient in the Al/SiC FGMs fabricated by CSPM and CMPM is developed. From the results, it is found that the volume fraction of SiC ceramic particles can be graded from the inner to the outer surface of hollow cylindrical shaped Al/SiC FGMs by CSPM. Meanwhile by CMPM, the SiC ceramic particles can be dispersed on the outer surface of hollow cylindrical shaped Al/SiC FGMs. The graded distribution in Al/SiC FGMs under huge centrifugal force is found to be significantly affected by the mold temperature but less affected by the temperature of molten Al and casting atmosphere.     

Computational fluid dynamic simulation of fluid flow in a rotating packed bed

Rotating packed bed (RPB) has been widely used in absorption, desorption, distillation, oxidation, crystallization, precipitation, polymerization, and production of nanoparticles. RPB utilizes centrifugal acceleration to intensify the mixing and mass-transfer processes. Under high-gravity, molecule diffusions are much faster than under normal gravity. With the centrifugal force generated by rotation, RPBs have considerable high mass-transfer and micromixing performance. However, because of the complexity of fluid flow inside the RPB, the flow experiments do not easily lead to the deeper understanding on the fluid dynamics in an RPB. In this paper, computational fluid dynamics model and two-, three-dimensional physical models have been developed to describe the RPB. Numerical simulation of the fluid flow and pressure drop in dry bed in an RPB using commercial software, Fluent, as a computational platform has been carried out. Different fluid flow rates, rotator speeds and gas flow rates have been systematically investigated. The preliminary simulation results show that the models used to describe the RPB can give rise to better understanding of the flow in an RPB.     

Advances in the Modeling and Measurement of Drained Compressibility

We have re-examined the analysis of centrifugal consolidation experiments for the determination of drained compressibility. Existing models for centrifugation of ceramic powder suspensions are prone to error, because they do not fully account for spatial variations of both the centrifugal acceleration and packing density. We present a new model that accounts for these two effects. We also derive dimensionless parameters that separately describe the error contributions that result from the heterogeneities of both the centrifugal acceleration and packing density. These dimensionless parameters make it no longer necessary to determine drained compressibility by the complicated method of nondestructively measuring the density profiles of centrifuge cakes and then substituting these profiles into a complex mathematical equation that is difficult to solve. Instead, one can evaluate drained compressibility by applying a correction factor to a simple experimental method of measuring the cake height during multispeed centrifugation. In turn, this procedure provides a valuable, new tool to characterize the effects of ceramic processing variables on their tendency to produce density gradients during powder consolidation.     

排气结构对PSC-100型导叶式旋风管内流场分布的影响

采用五孔球探针测量了不同排气结构参数(导流锥下口直径d1、开缝面积比a和开缝位置)的改变对PSC-100型导叶式旋风管内总压降和流场的影响.试验结果表明:带有导流锥的排气结构对分离有利;导流锥下口直径增大,气流旋转强度减小,颗粒分离所需离心力场减弱;导流锥开缝面积越大,分离空间内气旋强度越低;导流锥上侧缝开缝部位对旋风...