Particle Shape Parameters Research Articles

Correlating Particle Shape Parameters to Bulk Properties and Load Stress at Two Water Contents

Correlating Particle Shape Parameters to Bulk Properties and Load Stress at Two Water Contents

Comprehension of viscous morphology—Evaluation of fractal and conventional parameters for rheological characterization of Aspergillus niger culture broth

The filamentous fungus Aspergillus niger is a widely used host in industrial processes from food, chemical to pharmaceutical industry. The most prominent feature of this filamentous microorganism in submerged cultivation is its complex morphology which comprises dense spherical pellets as well as viscous elongated filaments. Depending on culture conditions, the exhibited morphology has tremendous effect on the overall process, making a precise understanding of fungal growth and morphology indispensable. Morphology, however, is only industrially relevant as long as it can be linked to important cultivation characteristics of filamentous microorganisms such as culture broth flow behavior. In the present study, different conventional and fractal morphological parameters gained from automatic image analysis were tested for their eligibility to predict culture broth rheology from morphologic appearance. The introduced biomass independent rheological parameters KBDW and nBDW obtained by power law relationship were successfully estimated from morphology related fractal and conventional parameters. For improved characterization of morphologic appearance of filamentous fungi newly introduced fractal quotient and lacunarity were compared to conventional particle shape parameters in form of the earlier established Morphology number (MN).

An inverse light scattering technique for morphological characterization of irregular particles based on the Gaussian-random-sphere model

The Gaussian-random-sphere model is employed for morphological characterization of nonspherical, irregular particles using an inverse light scattering technique. The synthetic measurement data consist of reduced scattering spectra caused by an aggregate of irregular particles randomly oriented in turbid media and are generated using the discrete dipole approximation. The proposed method simultaneously retrieves the concentration and shape parameters of particles using the data collected at multiple wavelengths. The performance of the inverse algorithm is tested using noise-corrupted data, in which up to 50% noise may be added to the observed scattering spectra.

Particle Shapes in the Drinking Water Filtration Process

AbstractDepth filtration is still one of the most important water treatment processes. It remains difficult to model mathematically because of the complexity of the process and the impact of numerous suspension parameters. The shape of the grains and suspension particles or flocs are among these parameters. The results of theoretical calculations suggest their visible impact on filtration. The shape of the media grain is relatively easy to measure. The shapes of the flocs or suspension particles, which are commonly not perfectly spherical, are much more difficult to predict. However, a few apparatuses developed lasting recent years make this possible. The FPIA 3000, manufactured by Malvern Instruments, uses flow particle image analysis method to measure 26 shape parameters of the suspension particles. Experimental measurement of suspension particle shape after flocculation and after depth filtration has allowed us to answer the question regarding the possible application of this measuring technique in water filtration technology. The experiments have also provided us with detailed information about the shape of flocs and suspension particles in filtered water. High number of particles characterized by circularity lower than 0.8 was detected in flocculated water inflowing to the filter. The particles remained in the outflow was characterized by visibly higher circularity than the particles inflowing to the filter. The results revealed much better removal of the particles characterized by lower circularity during filtration, whereas relation between convexity of the particles and their removal efficiency was not so evident.

Correlating Particle Shape Parameters to Bulk Properties and Load Stress at Two Water Contents

Particle shape of prospective root‐zone sands is evaluated qualitatively, but a quantitative shape determination may be more useful for sand selection. The objectives of this research were to: determine how particle shape complexity relates to bulk density, total porosity, and mechanical behavior (resistance to displacement given a vertical load); correlate quantitative shape parameters to these properties; determine how water content influences these relationships; and establish if quantitative shape parameters can be used to predict mechanical behavior in the absence of turfgrass roots. Seven materials of various shapes were separated into the medium size class (0.25–0.50 mm) to limit variability introduced by particle size distribution. A dynamic, digital imaging machine was used to quantify particle sphericity, symmetry, and aspect ratio. Bulk density, total porosity, and stress at multiple displacements were determined for the materials at two water contents, oven‐dry and 5% gravimetric water content. As sphericity, symmetry, and aspect ratio increased, bulk density increased and total porosity decreased. Sphericity, symmetry, and aspect ratio were negatively correlated with stress under a vertical load. The addition of water at compaction did not affect the correlations of the shape parameters with either bulk density or porosity; correlations of symmetry and sphericity with these were stronger at 5% water content for some displacements. Multiple regression analysis indicated that sphericity can be used to predict stress characteristics of sands compacted at 5% water content for specific testing conditions. These data indicate that particle shape complexity is related to bulk properties and has potential for predicting the stress characteristics of prospective root zone materials before construction.

Morphology engineering - Osmolality and its effect on Aspergillus niger morphology and productivity

BackgroundThe filamentous fungus Aspergillus niger is a widely used strain in a broad range of industrial processes from food to pharmaceutical industry. One of the most intriguing and often uncontrollable characteristics of this filamentous organism is its complex morphology, ranging from dense spherical pellets to viscous mycelia depending on culture conditions. Optimal productivity correlates strongly with a specific morphological form, thus making high demands on process control.ResultsIn about 50 2L stirred tank cultivations the influence of osmolality on A. niger morphology and productivity was investigated. The specific productivity of fructofuranosidase producing strain A. niger SKAn 1015 could be increased notably from 0.5 to 9 U mg-1 h-1 around eighteen fold, by increasing the culture broth osmolality by addition of sodium chloride. The specific productivity of glucoamylase producing strain A. niger AB1.13, could be elevated using the same procedure. An optimal producing osmolality was shown to exist well over the standard osmolality at about 3.2 osmol kg-1 depending on the strain. Fungal morphology of all cultivations was examined by microscope and characterized by digital image analysis. Particle shape parameters were combined to a dimensionless Morphology number, which enabled a comprehensive characterization of fungal morphology correlating closely with productivity. A novel method for determination of germination time in submerged cultivations by laser diffraction, introduced in this study, revealed a decelerated germination process with increasing osmolality.ConclusionsThrough the introduction of the versatile Morphology number, this study provides the means for a desirable characterization of fungal morphology and demonstrates its relation to productivity. Furthermore, osmolality as a fairly new parameter in process engineering is introduced and found to affect fungal morphology and productivity. Osmolality might provide an auspicious and reliable approach to increase the productivity in industrial processes. Because of the predictable behavior fungal morphology showed in dependence of osmolality, a customization of morphology for process needs seems feasible.

Simple models for the estimation of shearing resistance angle of uniform sands

Angle of shearing resistance is the key for the strength analysis of soils, since this parameter is commonly used for the description of shear strength of a soil. Many factors including soil mineralogy, particle shape, grain size distribution, void ratio, organic content, as well as water existence are effective on this parameter. Use of shear box tests for the determination of angle of shearing resistance is prevalent in geotechnical engineering practice, since it is rather successful in identification of shear strength of granular media. However, for cases in which shear box tests exhibit unreliable outcomes, alternative methods for the determination of this parameter could be beneficial. In this investigation, a number of nonlinear multiple regression, adaptive neuro-fuzzy inference systems, and artificial neural network (ANN) models are employed for the estimation of estimating the angle of shearing resistance of uniform sands by means of several grain size distribution, particle shape, and density parameters. Data including results of 132 shear box tests, particle shape identifiers, and grain size distribution parameters on uniform sands are used in the models. In training sessions, results of 104 tests are selected randomly and the results of remaining 28 tests are considered for testing sessions. The results revealed that the performance of a simple ANN architecture is sufficient for pre-evaluation of shearing resistance angle of uniform sands with the help of selected parameters. Since generalization of these models necessitates vast amount of experiments, great care should be dedicated on the assessment of similarity of training as well as testing data.

Effect of particle shape on density and permeability of sands

Particle shape is widely considered to be one of the most important factors affecting the behaviour of granular soils. This effect may change, based on variations in the grain size distribution. Therefore the effect of particle shape on the behaviour of granular soils should be investigated in soils of similar gradations. In this study, 20 different sands of five origins are initially subjected to image analyses in order to obtain data concerning shape characteristics. Then Proctor tests at three energy levels are conducted to obtain the densification characteristics of these soils. Basic statistical analyses are employed to obtain the distributions that the particle shape characteristics best fit. Empirical equations are developed to estimate the relative density of sands. Constant-head permeability tests are performed to determine the most suitable empirical formula for estimating the coefficient of permeability for granular soils. A new method for obtaining the shape coefficient for the Kozeny–Carman equation is proposed. Overall, relationships between a number of particle shape and fractal dimension parameters, as well as several statistics related to the relative density and permeability of soils, are investigated within an experimental framework.

On the effect of considering more realistic particle shape and mass parameters in MMOD risk assessments

One of the primary mission risks tracked in the development of all spacecraft is that due to micro-meteoroids and orbital debris (MMOD). Both types of particles, especially those larger than 0.1 mm in diameter, contain sufficient kinetic energy due to their combined mass and velocities to cause serious damage to crew members and spacecraft. The process used to assess MMOD risk consists of three elements: environment, damage prediction, and damage tolerance. Orbital debris risk assessments for the Orion vehicle, as well as the Shuttle, Space Station and other satellites use ballistic limit equations (BLEs) that have been developed using high speed impact test data and results from numerical simulations that have used spherical projectiles. However, spheres are not expected to be a common shape for orbital debris; rather, orbital debris fragments might be better represented by other regular or irregular solids. In this paper we examine the general construction of NASA’s current orbital debris (OD) model, explore the potential variations in orbital debris mass and shape that are possible when using particle characteristic length to define particle size (instead of assuming spherical particles), and, considering specifically the Orion vehicle, perform an orbital debris risk sensitivity study taking into account variations in particle mass and shape as noted above. While the results of the work performed for this study are preliminary, they do show that continuing to use aluminum spheres in spacecraft risk assessments could result in an over-design of its MMOD protection systems. In such a case, the spacecraft could be heavier than needed, could cost more than needed, and could cost more to put into orbit than needed. The results obtained in this study also show the need to incorporate effects of mass and shape in mission risk assessment prior to first flight of any spacecraft as well as the need to continue to develop/refine BLEs so that they more accurately reflect the shape and material density variations inherent to the actual debris environment.

Modeling and interpretation of extinction spectra of oriented nonspherical composite particles: application to biological cells

The majority of cells and microorganisms have a nonspherical shape and complex structure that challenge the interpretation of their spectral features. To address this issue, two approximations to the core-shell Mie theory were proposed. These included the approximation of light extinction by an ellipsoid with representation of the extinction by an equivalent sphere and representation of the extinction by a population of ellipsoidal particles with those of two weighted particle orientations. These hypotheses were first tested through numerical interpretation of the theoretical extinction spectra of prolate nucleated ellipsoids mimicking biological cells generated with anomalous diffraction approximation used as a reference method. Theoretical cases of fixed and random particle orientations demonstrated excellent capabilities of the proposed approach to retrieve the size, shape, and composition parameters of the model particles. Second, the UV-visible spectra of Leishmania species, promastigotes, elongated cells with prominent nuclei, were interpreted. The retrieved estimates of the protozoa size, shape, nucleus size, and nucleotide composition were in agreement with the corresponding microscopy estimates and literature values. Both theoretical tests and experimental results illustrated that the proposed approach can be successfully applied to estimate the structural and compositional parameters of cells from spectroscopic measurements.

Estimation of rock-aggregate volume based on PCA and LM-optimized neural network

In granule processing industries, acquisition of particle size and shape parameters is a common procedure, and volumetric measurement is of great importance in dealing with particle sizing and gradation. To eradicate the major drawbacks with manual gauge, this paper proposes an optical approach using Back Propagation (BP) neural network to estimate the particle volume based on the two-Dimensional (2D) image information. To achieve the better network efficiency and structure simplicity, Principal Component Analysis (PCA) is adopted to reduce the dimensions of network inputs. To overcome the shortcomings of generic BP network for being slow to converge and vulnerable to being trapped in local minimum, Levenberg-Marquardt (LM) algorithm is applied to achieve a higher speed and a lower error rate. The real particle data is utilized in training and testing the presented network. The experimental result suggests that the proposed neural network is capable of estimating aggregate volume with satisfactory precision and superior to the generic BP network in terms of performance capacity.

Improvements for ground-based remote sensing of atmospheric aerosol properties by additional polarimetric measurements

We discuss the improvements in the aerosol properties characterization resulting from the additional multi-wavelength polarization measurements measured by a new CIMEL polarized sun/sky-photometer, CE318-DP. In order to process direct-sun, sky and polarization measurements in a wide spectral range (340–1640 nm), we developed new calibration methods and strategies, e.g. using the Langley plot method to calibrate both direct-sun irradiance and sky radiance, as well as combining laboratory facilities with a vicarious method to calibrate the polarized sky measurements. For studying the impact of new polarimetric measurements on the retrievals of aerosol properties, we have processed an extensive record of field measurements using an updated Dubovik and King retrieval algorithm [Dubovik O, Sinyuk A, Lapyonok T, Holben BN, Mishchenko MI, et al. Application of spheroid models to account for aerosol particle nonsphericity in remote sensing of desert dust. J Geophys Res 2006;111:D11208.]. A preliminary analysis shows that adding polarization in the inversion can reduce possible errors (notably for about 30% of our field cases) in the fine mode size distribution, real part of refractive index and particle shape parameter retrievals, especially for small particles.

히스토그램에 의한 마멸분의 형태분포에 관한 연구

The wear particles are relative to the failure and the life of machine elements directly. But it is not laid down to calculate shape parameters of wear particle. To analyze a variation of distributed characteristics of wear particles on moving conditions, its shape parameters such as diameter and roundness were calculated the quantitative values by digital image processing, and had to be defined the effective method of using those data. Up to the present, the shape parameters have been used simply into the average values. But these values are not effective to analyze a variation of distributed characteristics of occurred wear particles on moving conditions. In this study, the relative histograms of shape parameters of wear particles were used for the purpose of analyzing the distribution of wear particles in various conditions. The results showed that the relative histogram of shape parameters can be effectively represented to study a wear mechanism.

Reconstruction of the Chicxulub ejecta plume from its deposits in drill core Yaxcopoil-1

Formation conditions of suevite-like impactites from an ∼100 m thick drill core sequence through the Cretaceous-Tertiary Chicxulub crater were reconstructed from empirical data obtained by petrologic and image analytical methods. The temporal evolution of the cratering process from the initial stage of excavation to the collapse of the ejecta plume is evidenced by the petrographic characteristics and modal composition of the suevitic rocks, including the size distribution and shape parameters of melt particles. Emplacement of the lowermost suevitic deposits likely started in the first minute after the impact by the passing ejecta curtain that interacted with the expanding ejecta plume. These ejecta deposits were capped by a tongue of coherent impact melt that was transported outward from the crater center during the collapse of the central uplift ∼5 min after impact. On top of this brecciated impact melt rock, the collapsing ejecta plume deposited air-fall suevites. The basal air-fall unit, Middle Suevite, may have been deposited due to a density current–like clumping of hot debris. With progressive cooling, regions of the ejecta plume were entrained in its collapse that produced vapor condensates, accretionary rims, and different oxygen fugacities. After cooling progressed, atmospheric conditions began to reestablish over the crater and turbulence decreased, supposedly after the first 10 min of initial ejecta plume collapse. This led to a winnowing out of fine matrix material and distinct sorting. However, due to aquatic reworking, only material that was deposited until ∼1 h after cessation of turbulent atmospheric conditions was retained.

Computer-controlled scanning electron microscopy (CCSEM) investigation of quartz in coal fly ash

Computer-controlled scanning electron microscopy (CCSEM) and X-ray diffraction (XRD) were used to investigate Si-rich phases in several coal fly ash (CFA) samples. The CCSEM measurements utilized both particle size distributions and a particle shape parameter, circularity, to classify the Si-rich phases in these ashes. The results indicated that the amount of free, respirable, crystalline quartz in these CFA samples was very small (<1.0 vol.% ). Neither the total quartz nor the respirable quartz determined by CCSEM showed a significant correlation with the XRD results for the bulk ash.

Correlation between the morphological characteristics and extinction spectra of sodium nanoparticles and modification of nanoparticles through photoatomic emission

The morphological characteristics of ensembles of metal nanoparticles on transparent dielectric substrates have been studied by the methods of hole-burning and linear absorption spectroscopy. The size and shape of particles were changed under the exposure to the optical radiation that induced photodetachment of atoms and their photostimulated diffusion over the surface of nanoparticles. The correlation between holes burned in different absorption bands is explained by the morphological features of the island film. The relaxation times of individual modes of collective plasma oscillations and the shape parameters of particles modeled by three-axial ellipsoids have been determined.

Distinguishing Respirable Quartz in Coal Fly Ash Using Computer-Controlled Scanning Electron Microscopy

Determination and classification of quartz in coal fly ash (CFA) is a subject of interest because of the adverse health effects caused by inhalation of crystalline silica. Workers with prolonged exposure to this carcinogen can develop respiratory diseases over time. This obviously may include utility plant workers involved in the handling, loading, and hauling of CFA. In this investigation, computer-controlled scanning electron microscopy (CCSEM) and X-ray diffraction (XRD) were used to investigate Si-rich phases in CFA to develop a better approach for the determination of respirable quartz. Three CFA samples from utility boilers and a NIST standard CFA sample were investigated. The XRD measurements indicated that the four samples contained from 7.0 to 16.0 wt.% of quartz. The CCSEM measurements utilized both particle size distributions and a particle shape parameter, circularity, to classify the Si-rich phases in these ashes as either crystalline or amorphous (glass). The results indicated that the amount of free, respirable, quartz in these CFA samples ranged from only 0.1-1.0 vol % and showed little correlation with the XRD results for the bulk ash. These results are significant in view of the factthat XRD is the traditional method of measuring crystalline silica in dust collected from workplace atmospheres.

Angularity evaluation of milled WC-Co powder

Technological properties of powders depend on their granularity and powder particle morphology. The grindability of hardmetal powder, the dynamics of milling and changes in particle granularity and morphology were studied. For particle morphology analysis the irregularity parameter as well as particle roundness and aspect ratio were found out. In order to characterise the granularity the mean particles size was measured and volume distribution function, median size and probability density function of the particles volume were calculated. For describing the angularity of milled powders so-called 'spike parameter - quadratic fit' (SPQ) was properly described and real experiments for determination of SPQ sensitivity and precision to characterise particles angularity were performed. Using the coefficients of variation for SPQ and particle shape parameters, the dispersions changes in dependence on the milling duration was investigated. Experiments for determination the influence of hardmetal particles angularity to erosion rate of different metallic materials show the essentiality of this parameter in powders shape characterisation.

3D Image Segmentation of Aggregates from Laser Profiling

Abstract: In digital imaging of discrete particles, such as stone aggregates, segmentation is one of the most important processes. Automated scanners of different designs use cameras or lasers to obtain digital images of groups of aggregate particles. To accurately determine particle size and shape parameters, each particle region in the image must be isolated and processed individually. Here, a method for segmenting a particle image acquired from laser profiling is developed using a Canny edge detector and a watershed transformation. Canny edges with rigorous and liberal threshold values are used to outline particle boundaries on a binary image and to check the validity of watersheds, respectively. To find appropriate regional minima in the watershed transformation, a varying search window method is used, where the number of neighboring pixels being compared with the pixel of interest is determined from the height value of the pixel. Test results with this method are promising. When implemented in automated systems that are designed to rapidly assess size and shape characteristics of stone particles, this technique can not only reduce the amount of time required for aggregate preparation, but also increase the accuracy of analysis results.

3D characterization of coarse aggregates

A new and accurate characterization method for dimensions, shape and roughness of aggregate particles has been developed. The method is based on the 3D-laser scanning technique and evaluation of coarse-grain aggregate-particle images. Parameters are obtained with either analytical Fourier analysis or geometrical analysis. The results from the two methods are compared with each other as well as with manual measurements. Although the Fourier-based analysis gives about 10% smaller size values, the comparison of the results shows, in general, a good agreement between the different techniques. This new method for analysis of coarse-grain aggregates gives reliable results for both the shape and topographical parameters of particles.