scholarly journals A General Method for Estimating Bulk 2D Projections of Ice Particle Shape: Theory and Applications

2019 ◽  
Vol 76 (1) ◽  
pp. 305-332 ◽  
Author(s):  
Edwin L. Dunnavan ◽  
Zhiyuan Jiang
Keyword(s):  
Aspect Ratio ◽  
Particle Shape ◽  
Ratio Distribution ◽  
Aspect Ratios ◽  
Shape Uncertainty ◽  
Aspect Ratio Distribution ◽  
Spheroidal Geometry ◽  
Orientation Parameters ◽  
General Method

Abstract The orientation of falling ice particles directly influences estimates of microphysical and radiative bulk quantities as well as in situ retrievals of size, shape, and mass. However, retrieval efforts and bulk calculations often incorporate very basic orientations or ignore these effects altogether. To address this deficiency, this study develops a general method for projecting bulk distributions of particle shape for arbitrary orientations. The Amoroso distribution provides the most general bulk aspect ratio distribution for gamma-distributed particle axis lengths. The parameters that govern the behavior of this aspect ratio distribution depend on the assumed relationship between mass, maximum dimension, and aspect ratio. Individual spheroidal geometry allows for eccentricity quantities to linearly map onto ellipse analogs, whereas aspect ratio quantities map nonlinearly. For particles viewed from their side, this analytic distinction leads to substantially larger errors in projected aspect ratio than for projected eccentricity. Distribution transformations using these mapping equations and numerical integration of projection kernels show that both truncation of size distributions and changes in Gaussian dispersion can alter the modality and shape of projection distributions. As a result, the projection process can more than triple the relative entropy between the spheroidal and projection distributions for commonly assumed model and orientation parameters. This shape uncertainty is maximized for distributions of highly eccentric particles and for particles like aggregates that are thought to fall with large canting-angle deviations. As a result, the methods used to report projected aspect ratios and the corresponding values should be questioned.

scholarly journals Atmospheric Ice Particle Shape Estimates from Polarimetric Radar Measurements and In Situ Observations

2017 ◽  
Vol 34 (12) ◽  
pp. 2569-2587 ◽  
Author(s):  
Sergey Y. Matrosov ◽  
Carl G. Schmitt ◽  
Maximilian Maahn ◽  
Gijs de Boer
Keyword(s):  
Aspect Ratio ◽  
Particle Shape ◽  
Characteristic Size ◽  
In Situ Measurements ◽  
Department Of Energy ◽  
Depolarization Ratio ◽  
Suggested Approach ◽  
Aspect Ratios ◽  
Radar Measurements

AbstractA remote sensing approach to retrieve the degree of nonsphericity of ice hydrometeors using scanning polarimetric Ka-band radar measurements from a U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program cloud radar operated in an alternate transmission–simultaneous reception mode is introduced. Nonsphericity is characterized by aspect ratios representing the ratios of particle minor-to-major dimensions. The approach is based on the use of a circular depolarization ratio (CDR) proxy reconstructed from differential reflectivity ZDR and copolar correlation coefficient ρhυ linear polarization measurements. Essentially combining information contained in ZDR and ρhυ, CDR-based retrievals of aspect ratios are fairly insensitive to hydrometeor orientation if measurements are performed at elevation angles of around 40°–50°. The suggested approach is applied to data collected using the third ARM Mobile Facility (AMF3), deployed to Oliktok Point, Alaska. Aspect ratio retrievals were also performed using ZDR measurements that are more strongly (compared to CDR) influenced by hydrometeor orientation. The results of radar-based retrievals are compared with in situ measurements from the tethered balloon system (TBS)-based video ice particle sampler and the ground-based multiangle snowflake camera. The observed ice hydrometeors were predominantly irregular-shaped ice crystals and aggregates, with aspect ratios varying between approximately 0.3 and 0.8. The retrievals assume that particle bulk density influencing (besides the particle shape) observed polarimetric variables can be deduced from the estimates of particle characteristic size. Uncertainties of CDR-based aspect ratio retrievals are estimated at about 0.1–0.15. Given these uncertainties, radar-based retrievals generally agreed with in situ measurements. The advantages of using the CDR proxy compared to the linear depolarization ratio are discussed.

Aspect Ratio Analysis Using Image Processing for Rice Grain Quality

2010 ◽  
Vol 6 (5) ◽  
Author(s):  
Amit K Aggarwal ◽  
Ratan Mohan
Keyword(s):  
Image Processing ◽  
Aspect Ratio ◽  
Local Market ◽  
Rice Grain ◽  
Ratio Analysis ◽  
Ratio Distribution ◽  
Aspect Ratios ◽  
Percent Accuracy ◽  
Aspect Ratio Distribution

Determination of aspect ratio distribution is important for elongated, needle-shaped particles whose utility and/or value may depend on this feature. In this work rice grain is taken as an example of such a particle and its aspect ratio distribution in various samples is found using image processing. The samples examined were from three different grades (commonly termed as full, half and broken) sold in local market and priced according to their size. From the analysis, reference aspect ratios were assigned to classify the grains and hence determine the extent of off-size in each market grade. Further, the effectiveness of the technique to quantify mixed or adulterated grades was studied. It was found that it is possible to know the undesired content within 10 percent accuracy.

Removing the Barriers to Next Generation'S Dielectric Films: In Situ Void-Free Planarized Films

1990 ◽  
Vol 203 ◽  
Author(s):  
J.R. Monkowski ◽  
M.A. Logan ◽  
L.F. Wright
Keyword(s):  
Aspect Ratio ◽  
Ion Chromatography ◽  
Field Measurements ◽  
Dielectric Films ◽  
Breakdown Field ◽  
Scanning Electron Micrographs ◽  
Aspect Ratios ◽  
New Process ◽  
Scanning Electron

ABSTRACTIn the next generation of semiconductor devices, minimum dimensions will be smaller, aspect ratios (height to width) of devices features will be larger, and BPSG dielectrics will be challenged to deal with these changes. A new process, which integrates deposition, flow, and anneal of BPSG films, and allows void-free filling of high-aspect-ratio trenches with excellent surface planarization, is presented in this paper. Scanning electron micrographs are used to show the extent of film coverage and planarization. Additional characterization includes ion chromatography, ellipsometry, stress measurements, and breakdown field measurements.

Solidification Processing Routes to High Aspect Ratio Reinforcements in γ-TiAl

1990 ◽  
Vol 194 ◽  
Author(s):  
J. J. Valencia ◽  
J. P. A. Löfvander ◽  
J. Rösler ◽  
C. G. Levi ◽  
R. Mehrabian
Keyword(s):  
Solid Solution ◽  
Aspect Ratio ◽  
Creep Strength ◽  
High Aspect Ratio ◽  
Anisotropic Growth ◽  
Solidification Processing ◽  
Aspect Ratios ◽  
The Matrix ◽  
Solute Strengthening

AbstractAdditions of ∼5%B1 and ∼9%Ta to binary γ-TiAl result in the formation of a monoboride isomorphous with TiB but containing Ta in solid solution. This boride exhibits strongly anisotropic growth from the melt, producing rod-like primary phases which are of potential interest for creep strengthening of the γ matrix. Fibrous borides with aspect ratios larger than ∼20 and volume fractions of ∼0.12 have been produced in arc-melted Ti-48AI-9Ta-4.3B alloys. Creep testing at 1255 K indicates that these “in-situ” composites have much higher creep strength than γ-TiAl, but the contribution of the reinforcements is relatively small compared with the solute-strengthening of the matrix.

scholarly journals Hydrometeor Shape Variability in Snowfall as Retrieved from Polarimetric Radar Measurements

2020 ◽  
Vol 59 (9) ◽  
pp. 1503-1517
Author(s):  
Sergey Y. Matrosov ◽  
Alexander V. Ryzhkov ◽  
Maximilian Maahn ◽  
Gijs de Boer
Keyword(s):  
Aspect Ratio ◽  
Doppler Radar ◽  
Particle Model ◽  
Polarimetric Radar ◽  
Aspect Ratios ◽  
Air Temperatures ◽  
Radar Measurements ◽  
Differential Reflectivity ◽  
Particle Shapes

AbstractA polarimetric radar–based method for retrieving atmospheric ice particle shapes is applied to snowfall measurements by a scanning Ka-band radar deployed at Oliktok Point, Alaska (70.495°N, 149.883°W). The mean aspect ratio, which is defined by the hydrometeor minor-to-major dimension ratio for a spheroidal particle model, is retrieved as a particle shape parameter. The radar variables used for aspect ratio profile retrievals include reflectivity, differential reflectivity, and the copolar correlation coefficient. The retrievals indicate that hydrometeors with mean aspect ratios below 0.2–0.3 are usually present in regions with air temperatures warmer than approximately from −17° to −15°C, corresponding to a regime that has been shown to be favorable for growth of pristine ice crystals of planar habits. Radar reflectivities corresponding to the lowest mean aspect ratios are generally between −10 and 10 dBZ. For colder temperatures, mean aspect ratios are typically in a range between 0.3 and 0.8. There is a tendency for hydrometeor aspect ratios to increase as particles transition from altitudes in the temperature range from −17° to −15°C toward the ground. This increase is believed to result from aggregation and riming processes that cause particles to become more spherical and is associated with areas demonstrating differential reflectivity decreases with increasing reflectivity. Aspect ratio retrievals at the lowest altitudes are consistent with in situ measurements obtained using a surface-based multiangle snowflake camera. Pronounced gradients in particle aspect ratio profiles are observed at altitudes at which there is a change in the dominant hydrometeor species, as inferred by spectral measurements from a vertically pointing Doppler radar.

Influence of Particle Shape and Contact Parameters on DEM-Simulated Bulk Density of Wheat

2020 ◽  
Vol 63 (6) ◽  
pp. 1657-1672
Author(s):  
Marvin C. Petingco ◽  
Mark E. Casada ◽  
Ronaldo G. Maghirang ◽  
Oladiran O. Fasina ◽  
Zhengpu Chen ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Bulk Density ◽  
Particle Shape ◽  
Static Friction ◽  
Rolling Friction ◽  
Particle Model ◽  
Dem Simulation ◽  
Aspect Ratios ◽  
Ellipsoidal Particles ◽  
Contact Parameters

HighlightsDecreasing aspect ratio and improved geometrical smoothness of particles increased DEM-predicted bulk density of wheat.Among the three particle models, the 5-sphere ellipsoidal particle was the best option to represent wheat particles, as indicated by the simulated bulk densities that best agreed with the experiments.Among the contact parameters, the wheat-to-wheat coefficient of static friction and wheat-surface coefficient of rolling friction had the greatest influence on simulated bulk density.Abstract. The discrete element method (DEM) has been shown to be an effective tool for simulating the behavior of granular material. The accuracy of simulations depends highly on the contact models, particle physical parameters, and contact parameters used. The objectives of this study were to determine the influence of particle shape and contact parameters on simulated wheat bulk density and to develop an effective wheat particle model for DEM simulation of filling a container using EDEM software. Grain characteristics, including single-kernel weight, kernel density, kernel dimensions, aspect ratio, and bulk density, were determined for three size fractions of wheat used in the experiments. Three categories of particle models (5-sphere pseudo-ellipsoidal, 7-sphere pseudo-ellipsoidal, and ASG-generated) with varying aspect ratios and geometrical smoothness were tested in the simulations. Results showed that DEM-simulated bulk density of wheat increased with lower aspect ratio and greater geometrical smoothness of pseudo-ellipsoidal particles (7-sphere versus 5-sphere). Increasing the number of spheres to approximately 30 for better representation of wheat kernel shape, using ASG-generated particles, did not reproduce the trend of greater simulated bulk density seen in the experiments. Among the six contact parameters, the wheat-wheat coefficient of static friction and wheat-surface coefficient of rolling friction had the most significant effect on the simulated bulk density. Among the different sets of particle models, the 5-sphere pseudo-ellipsoidal particles, having aspect ratios close to that of wheat kernels in each size fraction, were found to be the most practical and appropriate particle model for use in DEM simulation of wheat bulk density. This study contributes to better understanding of the influence of particle shape and contact parameters on DEM-simulated bulk density and provides a calibrated particle model for use in simulating container filling operations. Keywords: Bulk density, Contact parameters, DEM, Particle shape, Wheat.

scholarly journals Proxy development: a new facet of morphological diversity in the marine diatom <i>Eucampia antarctica</i> (Castracane) Mangin

2014 ◽  
Vol 33 (2) ◽  
pp. 131-142 ◽  
Author(s):  
Claire S. Allen
Keyword(s):  
Aspect Ratio ◽  
Austral Summer ◽  
Morphological Diversity ◽  
Polar Front ◽  
Marine Diatom ◽  
Morphological Data ◽  
Ratio Distribution ◽  
Amundsen Sea ◽  
Aspect Ratios ◽  
Sw Atlantic

Abstract. The varied aspect ratios observed in the Antarctic marine diatom Eucampia antarctica are described and quantified. Data are compiled from detailed measurements of the gross morphology of winter stage specimens found in samples of modern marine sediments. Surface sediment samples come from a range of oceanographic settings spanning almost 20° of latitude from north of the Polar Front in the SW Atlantic to close to continental Antarctica in the southern Amundsen Sea. Results are compared with previously recorded morphological data ascribed to the polar and sub-polar varieties of E. antarctica (E. antarctica var recta and E. antarctica var antarctica) and reveal that the aspect ratio of both varieties responds independently of symmetry and colony structure. The discussion considers the likely basis of the observed aspect ratio distribution and whether the morphological diversity offers any potential for use as proxy evidence in Antarctic palaeoceanographic reconstructions. Although it requires further study, valve symmetry offers promising potential as a quantitative proxy for austral summer sea surface temperatures.

scholarly journals Preload-responsive adhesion: effects of aspect ratio, tip shape and alignment

2013 ◽  
Vol 10 (83) ◽  
pp. 20130171 ◽  
Author(s):  
Dadhichi Paretkar ◽  
Marleen Kamperman ◽  
David Martina ◽  
Jiahua Zhao ◽  
Costantino Creton ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Compressive Stress ◽  
Polymer Surfaces ◽  
Buckling Instability ◽  
Aspect Ratios ◽  
Mechanical Buckling ◽  
Very High

We tested the adhesive response of polymer surfaces structured with arrays of cylindrical fibrils having diameters of 10–20 µm and aspect ratios 1–2.4. Fibrils had two different tip shapes of end-flaps and round edges. A preload-induced mechanical buckling instability of the fibrils was used to switch between the states of adhesion and non-adhesion. Non-adhesion in fibrils with round edges was reached at preloads that caused fibril buckling, whereas fibrils with end-flaps showed adhesion loss only at very high preloads. The round edge acted as a circumferential flaw prohibiting smooth tip contact recovery leading to an adhesion loss. In situ observations showed that, after reversal of buckling, the end-flaps unfold and re-form contact under prevailing compressive stress, retaining adhesion in spite of buckling. At very high preloads, however, end-flaps are unable to re-form contact resulting in adhesion loss. Additionally, the end-flaps showed varying contact adaptability as a function of the fibril–probe alignment, which further affects the preload for adhesion loss. The combined influence of preload, tip shape and alignment on adhesion can be used to switch adhesion in bioinspired fibrillar arrays.

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