Showing papers in "Particle & Particle Systems Characterization in 2008"
TL;DR: In this paper, the precision of the DLS technique for sizing polystyrene latex suspensions and the uncertainty of the data are estimated, and consistent values of mean particle diameter are found to be between those obtained by DLS and DMA within the estimated uncertainties.
Abstract: Dynamic light scattering (DLS) is a powerful technique for the sizing of nanoparticles and characterization of their properties in the liquid phase. However, the precision of this technique remains unclear and therefore, in the current work, the precision of the DLS technique for sizing polystyrene latex suspensions and the uncertainty of the DLS data are estimated. Precise measurements of the short time correlation function at seven scattering angles and five different concentrations are performed for four kinds of polystyrene latex suspensions with diameters of 30–100 nm. The extrapolations of apparent diffusion coefficients to infinite dilution and to lower angles yield more precise values than those obtained at one angle and one concentration. The extrapolated particle size measured by DLS is compared to the size determined by a differential mobility analyzer (DMA) in air. Before the comparison, the intensity-averaged size measured by DLS is recalculated to the number-averaged size in the case of DMA from the particle size distribution. After the recalculation, consistent values of mean particle diameter are found to be between those obtained by DLS and DMA within the estimated uncertainties.
91 citations
TL;DR: In this paper, the structure of different pyrogenic silica grades has been characterized by static light and X-ray scattering and the diffusional properties were obtained by multi-angle DLS measurements.
Abstract: Dynamic light scattering (DLS) is frequently used to characterize suspensions of pyrogenic silica which consists of polydisperse fractal aggregates of sintered spherical primary particles. As the method primarily measures temporal fluctuations of scattered light caused by the translational and rotational diffusive motion of the aggregates it is an important prerequisite to identify those structural properties that are measurable with DLS and to quantify the method’s sensitivity to changes in these properties. In a recent paper [1] we have investigated the structure-hydrodynamics relationship via simulations. Here, the validation of the simulation results by experimental data is presented. Therefore, the structure of different pyrogenic silica grades has been characterized by static light and X-ray scattering and the diffusional properties were obtained by multi-angle DLS measurements. It is shown that the hydrodynamic radii determined with DLS scale well with the mean aggregate radius of gyration but that the influence of rotational diffusion has to be accounted for in the measurements.
61 citations
TL;DR: The applicability of different inversion algorithms to retrieve a size distribution of particles in air from light scattering is examined in this article, where the authors focused on an optical measurement setup with an elliptical mirror as the main optical element.
Abstract: The applicability of different inversion algorithms to retrieve a size distribution of particles in air from light scattering is examined. The investigation is focused on an optical measurement setup with an elliptical mirror as the main optical element. In order to evaluate the capabilities of the individual inversion methods, light scattering by spherical particles is simulated in the size ranges of 0.1 – 10 μm and 0.05 – 1 μm. The distribution of the particle diameters is modeled with three different parametric functions, i.e., RRSB, logarithmic-normal and a more specific distribution from an ultrasonic nebulizer. Different kinds of noise, e.g., additive and/or multiplicative, are applied in different levels to the simulated scattering measurement to include real physical measurement conditions. The convergence properties of the scattering simulation are investigated with respect to the number of size classes, and thus, information concerning the size resolution required to simulate a measurement for a given particle size distribution is obtained. Further parameters of interest are the minimum angular resolution of the measurements, the number of size classes of the retrieved particle size distribution and the measured polarization of the scattered light.
46 citations
TL;DR: In this article, a review of previous work undertaken using electrical resistance tomography (ERT) for applications associated to wet particulate processing is presented. And the review is split into three sections including multi-phase flow, solid-liquid suspensions and reactive particulate processes.
Abstract: Electrical Resistance Tomography (ERT) provides the capability to measure the conductivity distribution within a given process plant delivering time evolving multi-dimensional information which often enhances fundamental process understanding whilst improving the design and operation of the process equipment. This paper reviews previous work undertaken using ERT for applications associated to wet particulate processing. The review is split into three sections including multi-phase flow, solid-liquid suspensions and reactive particulate processing. Typical results from a number of examples from both, research and industrial environments are presented.
42 citations
TL;DR: In this paper, an algorithm is developed that enables the generation of aggregates with a tunable fractal dimension and an arbitrary number of primary particles, which is of great relevance for the interpretation of DLS results.
Abstract: Dynamic light scattering (DLS) is a method used to size nanoscale and submicron particles by measuring their thermal motion (diffusion) in a liquid environment. The measured diffusion coefficients are related to the hydrodynamic particle size via the Stokes-Einstein equation. This paper addresses the application of DLS for the characterization of diluted suspensions of pyrogenic silica, which consist of polydisperse fractal-like aggregates composed of sintered spherical primary particles. Simulations are employed to establish a relationship between the structural properties of the aggregates and their diffusional behavior. Therefore, an algorithm is developed that enables the generation of aggregates with a tunable fractal dimension and an arbitrary number of primary particles. The results provide evidence that the hydrodynamic radii show a different scaling compared to the structural radius of gyration, which is of great relevance for the interpretation of DLS results. In addition, the influence of rotational diffusion has to be accounted for in the measurements.
37 citations
TL;DR: In this paper, the properties of four crystalline materials (two proteins, Lysozyme and glucose isomerase and two non-proteins, glutamic acid and potassium sulphate) were measured with an indentation technique.
Abstract: The mechanical properties (critical stress intensity factor, hardness and Young's modulus) of 4 crystalline materials (two proteins, lysozyme and glucose isomerase and two non-proteins, glutamic acid and potassium sulphate) were measured with an indentation technique. It was found that the mechanical properties of lysozyme crystals depend on their state - dried, partly dried and moisture saturated - and their surroundings. The hardness, Young's modulus and the critical stress intensity factor of lysozyme crystals were observed to be much lower than those for the tested non-proteins, leading to the conclusion that crystalline lysozyme is comparatively more fragile and softer. In combination the mechanical properties of lysozyme and the non-proteins indicated that these materials were fairly brittle. Mechanical properties for crystals of the other protein, glucose isomerase, could not be quantified by indentation. However, qualitatively crystalline glucose isomerase was found to be more ductile and less fragile than crystalline lysozyme. The experimental findings were interpreted in terms of relative susceptibility to attrition and secondary nucleation in stirred industrial crystallizers.
34 citations
TL;DR: In this article, the authors evaluate possible corrections that could be applied to the classical Rayleigh-Debye-Gans for Fractal Aggregates (RDG-FA) formula in order to take into account of aggregates and primary particles internal multiscattering.
Abstract: The characterization of soot fractal aggregate, i.e., morphology, size, number and volume fraction, by optical diagnostics is very widespread since it is a sensitive and nonintrusive technique. In general, light absorption or scattering by fractal aggregates is quantitatively interpreted by the Rayleigh-Debye-Gans for Fractal Aggregates (RDG-FA) theory due to its simplicity. Nevertheless, important conditions have to be obeyed for the correct use of this theory. Among them, aggregates and primary particles have to be very small in comparison to the wavelength. In addition, internal scattering must be negligible. Moreover, the form factor functions that allow the fractal morphology to be taken into account have been established for a polydispersed population. In contrast to previous studies that evaluated the valid RDG-FA range by comparing the difference between rigorous calculations and the RDG-FA approach, the aim of the present study is to evaluate possible corrections that could be applied to the classical RDG-FA formula in order to take into account of aggregates and primary particles internal multiscattering. Therefore, new generalized form factors are proposed allowing the evaluation of the optical properties of one aggregate with a primary particle diameter of up to 90 nm, without any assumptions concerning aggregate complex internal interactions. The presented results are based on the assumption that DDSCAT (Discrete Dipole Approximation) provides accurate results, with a wavelength, λ = 632 nm, a soot fractal dimension of 1.8 and Dalzel and Sarofim optical index, m = 1.57 – i0.56.
34 citations
TL;DR: In this article, the authors describe the generation of small water droplets in the size range down to a few microns using a new and more sophisticated computer-based signal generation system.
Abstract: This paper describes the generation of small water droplets in the size range down to a few microns. Commercially available inkjet printing devices are not suitable for producing such droplets since they produce satellite droplets. Furthermore, standard drop-on-demand devices are normally restricted to the generation of droplets with the same size as the orifice diameter. Using a new and more sophisticated computer-based signal generation system, smaller-sized droplets can be generated from the same orifice. A key feature of the design is the generation of freely definable pulses. This enables the generation of acoustic modes within the fluid of the droplet generator, which leads to the generation of droplets without satellites. Only very few pulse forms enable the generation of suitable acoustic modes. Therefore, it is necessary to look for the specific pulse corresponding to the chosen droplet generator. Flexible pulse form generation appears to be more suitable than simple pulse forms for the generation of such droplets.
33 citations
TL;DR: In this article, a system for simultaneous three-dimensional measurement of particle shape has been developed based on a free-fall analysis, which can be used for particle characterization as well as for simulations of particle behavior.
Abstract: A system for simultaneous three-dimensional measurement of particle shape has been developed. The system is based on a free-fall analysis. Free-falling particles are captured from three orthogonal directions and reconstructed in the three-dimensional sense. The three-dimensional information can be used for particle characterization as well as for simulations of particle behavior.
32 citations
TL;DR: In this article, an original concept for automatic determination of the time intervals for calculation of the mass flow rate of intermittent flow using a twin-plane electrical capacitance tomography system was presented.
Abstract: This paper presents an original concept for automatic determination of the time intervals for calculation of the mass flow rate of intermittent flow using a twin-plane electrical capacitance tomography system. The concept allows a solids mass flow rate to be calculated more accurately. It is based on images of instantaneous distributions of the material inside the measured volume by means of Electrical Capacitance Tomography (ECT), and extraction of the appropriate flow patterns, which are further used for calculation of the mass flow rate. The preliminary results of the mass flow rate measurement using the proposed concept for gas-solid flow during pneumatic conveying are presented.
24 citations
TL;DR: In this paper, a lumped mechanistic model has been developed to describe the heat and mass transfer between solid, gas and bubble phases in a batch fluidized bed dryer.
Abstract: In this work, a lumped mechanistic model has been developed to describe the heat and mass transfer between solid, gas and bubble phases in a batch fluidized bed dryer. To minimize the computational load, an approximation of the bubble temperature has been made in the model and it is shown that this does not significantly reduce the accuracy of the model. Model parameter sensitivity analysis has indicated that the performance characteristics of a bath fluidized bed dryer are affected not only by the inlet gas superficial velocity and temperature, but also by the features of particle and bubble phases, in particular, the particle and bubble sizes. Experimental validation shows that the proposed lumped dynamic model can be used to predict the particle moisture content and temperature profiles during the drying process in a fluidized bed dryer.
TL;DR: The three-parameter, generalized gamma function solution of a recent MEF formulation used to derive liquid spray drop-size distribution, is applied to sprays resulting from three different atomization processes as mentioned in this paper.
Abstract: The three-parameter, Generalized Gamma function solution of a recent MEF formulation used to derive liquid spray drop-size distribution, is applied to sprays resulting from three different atomization processes. The objectives of these applications are to determine the sign of the parameters for which this function reports a more reliable fit and to further understand the parameter stability problem reported elsewhere. It is found that the lack of stability of the parameters is related to a characteristic feature of the mathematical function and appears for a series of spray drop-size distributions with constant shape. For each situation analyzed in the present study, the Generalized Gamma function provides a very good fit with parameters that are either constant or correlated to the working conditions. As far as the sign of the parameters is concerned, the results show that the best formulation is a function of the spray and that it is impossible to know, a priori, which parameter sign will report the best fit. Finally, for one situation, it is found that the Generalized Gamma function allows extrapolation of drop sizes outside the measured values. All of the results converge to conclude that the three-parameter Generalized Gamma function, which is identical to the well-known Nukiyama-Tanasawa distribution, accumulates valuable attributes to represent liquid spray drop-size distributions.
TL;DR: In this article, the use of NIR for monitoring batch cooling crystallization processes, and emphasis is placed on applying genetic algorithm (GA) for wavelength selection in partial least squares calibration model development.
Abstract: Near infrared spectroscopy (NIR) uses fiber-optics for rapid data transmission, is robust, simple, and sensitive at both low and high solution concentrations. Therefore, it is particularly suitable for monitoring industrial processes. This study investigates the use of NIR for monitoring batch cooling crystallization processes, and emphasis is placed on applying genetic algorithm (GA) for wavelength selection in partial least squares calibration model development. The calibration data was collected for under-saturated and saturated solutions, as well as for α- and β-form crystal slurries of L-glutamic acid at a variety of solution concentrations, temperatures, and solid concentrations and sizes. The GA method proves to be capable of effectively selecting a small number of wavelengths and the models thus developed give improved prediction performance in terms of generalization capability compared to models derived using the full spectrum. The developed models are successfully applied to monitoring batch cooling crystallization of L-glutamic acid under seeded and unseeded conditions and with varied cooling rates.
TL;DR: In this paper, an estimator for particle number density that accounts for both edge effects and particle overlap is presented, using the output of advanced image analysis applied to artificial images, the estimator is shown to enable effective estimation of PSD for monodisperse particulate systems at high densities.
Abstract: Particle number density measurements obtained by image analysis are biased by edge effects and particle overlap. This paper presents an estimator for particle number density that accounts for both edge effects and particle overlap. Using the output of advanced image analysis applied to artificial images, the estimator is shown to enable effective estimation of particle number density for monodisperse particulate systems at high densities. This paper also proposes a single dimensionless number that correlates with the reliability of the inferred PSD based on the likely number of overlaps per particle. As this dimensionless group becomes large, the degree of overlap and occlusion in the images makes image analysis difficult and unreliable. This parameter can aid practitioners in finding the proper sampling conditions to obtain accurate PSD measurements.
TL;DR: In this paper, the authors consider the problem of particle sizing in DLS and propose a measurement system that minimizes the amount of noise in the measurement system by selecting the optical components carefully to minimize the noise from the unit itself.
Abstract: In order to acquire high quality measurement data from DLS (Dynamic Light Scattering) experiments, serious attention has to be paid to minimizing the noise involved. In this paper, the noise in DLS for particle sizing is addressed for four parts of the measurement system. The first is the noise caused from the low quality of sample preparation and the scattering medium containing too high or too low concentration of analyte. The second is from the view of optics, i.e., the laser must have sufficient power, be stable under all expected conditions, and usually be restricted to a single transverse mode, in case it causes distortion in measurement data. In addition, if the energy of the incident light is too high, strong absorption occurs, which will induce thermal blooming. The optical components must be carefully chosen and designed to minimize noise from the unit itself. The detection area should be calculated to reach the best signal-to-noise ratio and an entrance lens with magnification that is too high and that causes distortion in the ACF (Auto Correlation Function) should be avoided. Some new components such as fiber optics and graded-index may also introduce new noise. The third factor is the photodetector, which must have adequate speed and sensitivity and possess suitably low internal correlations and noise. In addition, the quantum noise from the detector should be subtracted. The fourth factor is that the correlator should be chosen carefully. In some cases, equipment with a higher speed and more channels should be chosen to minimize the statistical noise.
TL;DR: In this article, a novel instrument was developed for the size analysis and concentration measurement of particles dispersed in gases at high temperatures (600 ˚C) and pressures (16 bar).
Abstract: Based on the findings of previous work, a novel instrument was developed for the size analysis and concentration measurement of particles dispersed in gases at high temperatures (600 °C) and pressures (16 bar). The main motivation for the construction of this device was a measurement requirement at the conditions of a pressurized pulverized coal combustion (PPCC) test installation in Dorsten, Germany. The development of a high efficiency (> 50 %), coal based, combined cycle process, and specifically, the development of efficient gas cleaning technology for gas combustion under demanding conditions (1400 °C and 16 bar) was the main target. A suitable measurement technique was required for the determination of particle size and concentration downstream of the gas cleaning equipment, which is able to operate close to the given conditions. The performance of the novel device was tested in several measurement series with various monodisperse aerosols at ambient conditions as well as in high pressure, high temperature situations with very satisfactory results, i.e., the lower detection limit (50 % counting efficiency at ca. 0.3 μm) and resolution of the novel device are comparable to state of the art instruments (of the same principle) intended for room temperature operation.
TL;DR: This paper considers electromagnetic wave scattering by aggregated fibres using a multiple scattering approach and proposes a decompositioning approach to handle this scattering problem.
Abstract: In this paper we consider electromagnetic wave scattering by aggregated fibres using a multiple scattering approach Scattering by particles of complex shape such as concave particles, torus, or clusters of fibres can not normally be computed using the T-matrix method In this paper we are proposing a decompositioning approach to handle this scattering problem A scattering particle is decomposed into a number of basic units and scattering by such an ensemble of basic constituents is computed using a multiple scattering T-matrix approach The range of validity of this approach is investigated by providing exemplary computation results for single fibres and aggregated fibres
TL;DR: In this paper, a new approach in data acquisition is presented to solve this problem at least partially, resulting in a global rainbow of mainly spherical particles, where images of the most spherical droplets are selected by using of certain criteria derived from computations of rainbows of single spheres using the Lorenz-Mie theory.
Abstract: Originally developed to measure the refractive index, global rainbow refractometry also permits the extraction of a size distribution. When this technique is applied to a spray with a large number of non-spherical particles, the number of small particles tends to be overestimated. A new approach in data acquisition is presented to solve this problem at least partially, resulting in a global rainbow of mainly spherical particles. Thus, measurement errors due to non-sphericity can be minimized. The global rainbow is constructed from an image series of rainbows of individual droplets, where images of the most spherical droplets are selected by use of certain criteria derived from computations of rainbows of single spheres using the Lorenz-Mie theory.
The method is tested with measurements in a spray. The mean droplet temperature and the size distribution, obtained from the inversion of the global rainbow, are compared to results obtained without using the selective imaging method and to results from other measurement techniques. The comparison of the results shows a better agreement when the selective imaging method is applied, especially for size distribution measurements close to the atomizer where a high amount of non-spherical droplets can be expected.
TL;DR: In this paper, the high level of hierarchical structural organization in the shells of marine organisms was studied, and calcite brachiopod shell materials were found to belong to three types of microstructure: nano-to micro-crystalline layers ofacicular crystals, fiber composites with calcite single crystal fibers with [uv0] morphological axes, and material formed by columnarcrystals with [001] morphology axes selected by competitive growth.
Abstract: Electron backscatter diffraction (EBSD) is an easy to use and highlyautomated microdiffraction method suitable for the determination ofcrystallographic phase and crystallite orientation. The high level ofhierarchical structural organization in the shells of marine organismswas studied. Calcite brachiopod shell materials were found to belong tothree types of microstructure: nano to microcrystalline layers ofacicular crystals, fiber composites with calcite single crystal fiberswith [uv0] morphological axes, and material formed by columnarcrystals with [001] morphological axes selected by competitive growth.
TL;DR: The DLS‐PM is introduced and the advantages and challenges for dynamic light scattering to become a clinically relevant, routinely used platelet test are discussed.
Abstract: Extension of the current 5-day shelf life of platelet concentrates to increase the supply of this life saving blood product will require quality testing. However, no automated test exists to routinely measure the quality of platelet concentrates for transfusion. Platelet concentrates cannot be sampled and diluted. These practical limitations have prevented the routine use of optical methods for platelet quality testing. The Dynamic Light Scattering Platelet Monitor (DLS-PM) addresses these limitations. The DLS-PM is a portable instrument with a temperature-controlled sample holder to accommodate a wide range of sample containers. The challenges of small sample size, short light path through the sample, and accurate temperature control have been solved. The DLS-PM measures platelet size, number of platelet-derived microparticles, and the response of platelets to temperature changes, which are combined to calculate a platelet quality score. In this paper we introduce the DLS-PM and discuss the advantages and challenges for dynamic light scattering to become a clinically relevant, routinely used platelet test.
TL;DR: Soule, Ezequiel Rodolfo, et al. as mentioned in this paper presented a model for the study of the relationship between the sciences and technology in the context of the Consejo Nacional de Investigaciones Cientificas and Tecnicas.
Abstract: Fil: Soule, Ezequiel Rodolfo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingenieria. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales; Argentina
TL;DR: In this article, an experimental investigation into the importance of illumination wavelength on measurement accuracy for an existing digital imaging based particle size analyzer is presented, where two sources of illumination were used - red and blue (625 and 470 nm), polymer micro-spheres in the 2.5-100 micron range, calibrated to NIST (National Institute of Standards and Technology) standards, were interrogated under static conditions.
Abstract: This paper presents the results of an experimental investigation into the importance of illumination wavelength on measurement accuracy for an existing digital imaging based particle size analyzer. When the system was originally developed, fairly large particles were interrogated rendering the effects of illumination wavelength insignificant, but recent work has suggested that there is an interest in the scientific community in analysing particles down to a few microns in size. At these scales illumination wavelengths and particle size are of similar magnitudes, possibly leading to problems. The work presented in this paper is intended to be a practical investigation into wavelength effects using the existing system. This aim has been met firstly by introducing the basic system, along with some key past results and accuracy, then moving on to explain the wavelength tests and present new results. Two sources of illumination were used - red and blue (625 and 470 nm), Polymer micro-spheres in the 2.5-100 micron range, calibrated to NIST (National Institute of Standards and Technology) standards, were interrogated under static conditions. It is shown that whilest blue illumination does give an increase in accuracy, the effect is not marked enough to preclude the use of cost-effective red illumination at these scales.
TL;DR: In this article, an integrated photodiodes-based optical flow cytometry system was proposed to obtain physical and chemical parameters of single biological cells in a flow-through setup by using optical measurement techniques.
Abstract: Optical flow cytometry is a process where physical and (bio-) chemical parameters of single biological cells can be obtained in a flow-through setup by optical measurement techniques. Unlike conventional systems, where measurements are conducted in the optical far field, the proposed system senses the cell's optical projection in the near field by using integrated photodiodes. This allows for the attainment of additional parameters, e.g., size and shape, which are usually hidden in the far field. In addition, parameters such as refractive index and absorption of the cell influence the sensor signal. Additionally, with another setup, a different approach is followed to measure similar parameters with external detection using a DVD laser pickup head and a microchannel equipped with a mirror. This low-cost setup does not measure in the near field, and therefore, is dedicated to different parameters. In this contribution, results from measurements with polystyrene particles and biological cells (yeast and Chinese hamster ovary) are presented and the advantages and limitations of both systems are outlined.
TL;DR: In this article, an experimental demonstration of a noncontact particle characterization technique called Aerodynamic Vectoring Particle Sorting (AVPS) is presented, which uses secondary blowing and suction control flows to sharply change the direction of a planar, particle-laden jet.
Abstract: An experimental demonstration of a new, non-contact particle characterization technique called Aerodynamic Vectoring Particle Sorting (AVPS) is presented. AVPS uses secondary blowing and suction control flows–flows that are a fraction of the jet flow rate–to sharply change the direction of a planar, particle-laden jet. As the jet is vectored, particles present in the flow experience a resultant drag force, dependent upon their size, that balances inertia. Since this balance determines the particle's trajectory, vectoring the flow leads to a separation of particles downstream. This simple, low-pressure-drop sorting technique classifies particles with less risk of damage or contamination than currently available sorting devices.
Particles from 10–40 μm and 2.5 times the density of water have been sorted to an accuracy of 1.5 μm. Sorting of heavy particles such as these is accomplished at very low speeds, reducing the tendency of damage to the particles. Lighter particles are sorted at higher speeds. Particles from 5–40 μm and 0.6 times the density of water were sorted to an accuracy of 6.6 μm.
AVPS is also shown to be capable of concentrating aerosols. Our measurements indicate that an air sample containing water-like particles can be concentrated by a factor of 10 using AVPS.
TL;DR: In this article, a q-space analysis of the light scattering data was performed for polydisperse powders of spherical shell particles and nonspherical, three dimensionally dense aggregates.
Abstract: Polydisperse powders of spherical shell particles and nonspherical, three dimensionally dense aggregates were dispersed as turbulent jets through an abrupt orifice nozzle and in-situ small angle light scattering measurements were made. In contrast to traditional studies, the light scattering data were plotted versus the scattering wave vector rather than the scattering angle; we call this q-space analysis. For dense aggregates distinct power law trends emerged, similar to those discovered previously for spherical Mie scatterers. Moreover, when the system was very polydisperse, either with a broad bimodal or monotonic with extreme range, the q-space analysis provided particle size distribution information about these aerosol systems which was unapparent when plotted as a function of the scattering angle.
TL;DR: The measurements were realized with temporal correlation of the transmission fluctuation signals of a focused Gaussian beam, whereby both particle-size distribution and particle concentration can be measured simultaneously.
Abstract: Transmission fluctuation spectrometry with temporal correlation (TFS-TC) is a new method for particle analysis. When a narrow light beam irradiates on a particle dispersion flow, the variation of the number of particles in the small measuring zone will cause the transmitted light to fluctuate, which includes the complete information on both particle size distribution (PSD) and particle concentration. The method may be used for real-time, inline/online applications due to its simplicity of measuring principle and experimental setup. Until recently, the theory has been limited to low particle concentrations. In this work, an experimental study of the TFS-TC measurement is presented for a very wide range of the particle concentrations. By introducing an empirical correction including the high concentration effects and considering the effect from rheological conditions in the inversion algorithm, the particle size distribution and particle concentration are reconstructed, resulting in the coverage of a broad range of particle size and concentration.
TL;DR: In this article, solid fully-filled zirconia particles were synthesized at relatively high reactor temperatures (∼ 400°C) by adding NaCl as impurities to Zirconium hydroxychloride (ZHC) precursor that would have lead to the formation of hollow disrupted particles otherwise.
Abstract: Using spray pyrolysis, solid fully-filled zirconia particles were synthesized at relatively high reactor temperatures (∼ 400 °C) by adding NaCl as impurities to zirconium hydroxychloride (ZHC) precursor that would have lead to the formation of hollow disrupted particles otherwise. FE-SEM images show that at comparable concentration of NaCl and ZHC both cubic and spherical NaCl/ZrO2 particles form. The particle characteristics were varied by varying solute concentration, type, and solvent content. Addition of NaCl caused the formation of both cubic and spherical particles which were non-disrupted at even high temperatures. According to the EDS compositional analysis, the cubic particles had more Na content while the spherical ones had higher Zr content. It is concluded that growth mechanism of NaCl particles is different from that of zirconia particles. Drying of the former even at high temperatures leads to the formation of solid, fully-filled, porous particles, whereas hollow, disrupted particles are formed using the latter.
TL;DR: Cl clustering approaches based on the fuzzy C‐means algorithm are employed to identify the touching particle regions and the technique is proven to minimize greatly the deleterious effects of over‐segmentation, as is the case with traditional watershed segmentation techniques.
Abstract: The occurrence of touching objects in images of particulate systems is very common especially in the absence of dispersion methods during image acquisition. The separation of these touching particles is essential before accurate estimation of particle size and shape can be achieved from these images. In the current work, clustering approaches based on the fuzzy C-means algorithm are employed to identify the touching particle regions. Firstly, clustering in the multidimensional space of image features, e.g., standard deviation, gradient and range calculated in a certain neighborhood of each pixel, is performed to trap the touching regions. Then, in a novel proposed method, the clustering of pixel intensity itself into two fuzzy clusters is performed and a feature, referred to as the ‘Fuzzy Range', is calculated for each pixel from its membership values in both clusters and is presented as a distinguishing feature of the touching regions. Both approaches are compared and the superiority of the latter method in terms of the non-necessity of neighborhood based calculations and minimum disfiguration is elucidated. The separation methods presented herein do not make any assumption about the shape of the particle as is undertaken in many methods reported elsewhere. The technique is proven to minimize greatly the deleterious effects of over-segmentation, as is the case with traditional watershed segmentation techniques, and consequently, it results in a superior performance.
TL;DR: The stability and robustness properties of the closed-loop system under the three predictive controllers are compared extensively under three different assumptions on how the measurements from the crystallizer are obtained.
Abstract: This work focuses on state feedback, model predictive control of particulate processes subject to asynchronous measurements. A population balance model of a typical continuous crystallizer is taken as an application example. Three controllers, i.e., a standard model predictive controller and two recently proposed Lyapunov-based model predictive controllers, are applied to stabilize the crystallizer at an open-loop, unstable steady-state in the presence of asynchronous measurements. The stability and robustness properties of the closed-loop system under the three predictive controllers are compared extensively under three different assumptions on how the measurements from the crystallizer are obtained.
TL;DR: In this article, a new concept to derive particle information from depolarization ratios obtained by a simultaneous three-wavelength lidar was presented, which utilized the wavelength dependence of the ratio of the polarization components in the scattering light based on T-matrix computation.
Abstract: A new concept to derive particle information from depolarization ratios obtained by a simultaneous three-wavelength depolarization lidar was presented. This new data treatment utilized the wavelength dependence of the ratio of the polarization components in the scattering light based on T-matrix computation. The results showed that calculated three-wavelength depolarization ratios can be used to characterize particle sizes of ice particles. Assessing the mixing of spherical and nonspherical aerosols, the presented method successfully reproduced the lidar data in real.