Calibrations and Performance of the Airborne Cloud Extinction Probe

Abstract A new airborne instrument that measures extinction coefficient β in clouds and precipitation has been designed by Environment Canada. The cloud extinction probe (CEP) utilizes the transmissometric method, which is based on direct measurement of light attenuation between the transmitter and receiver. Transmissometers are known to be susceptible to forward scattering, which becomes increasingly significant as the particle size increases. A new technique for calibrating transmissometers was developed here in order to determine the response function of the probe. Laboratory calibrations show that CEP-derived β may be underestimated by a factor of 2 for circular particles with diameters greater than 100 μm. Results for spherical particles are in good agreement with theoretical predictions. For nonspherical particles, however, estimates of β can deviate significantly from those derived for spheres that have the same projected area. For in situ observations of ice particles, CEP measurements often deviate significantly from theoretical calculations, whereas for small cloud droplets agreement is good. It is hypothesized that CEP-derived estimates of β for ice clouds depend much on variations in the scattering phase function that arise from details in ice crystal surface roughness and fine crystal structure. This would complicate greatly the estimation of β from transmissometers for ice-bearing clouds.

Download Full-text

Techniques for Determining the Parameters of a Two-Dimensional Tire Model for the Study of Ride Comfort

Tire Science and Technology ◽

10.2346/1.2137540 ◽

1997 ◽

Vol 25 (3) ◽

pp. 187-213 ◽

Cited By ~ 7

Author(s):

F. Mancosu ◽

G. Matrascia ◽

F. Cheli

Keyword(s):

Physical Properties ◽

Ride Comfort ◽

Dynamic Test ◽

Longitudinal Direction ◽

Tire Model ◽

Rigid Ring ◽

Ring Model ◽

Mass Moment ◽

A New Technique ◽

And Performance

Abstract A rigid ring model of the tire for the study of in-plane dynamics and a new technique for determining the parameters of the model are presented in this paper. This model can be used for studying the comfort of vehicles, problems of driving, and braking problems in the longitudinal direction. Comparison with finite element models shows that the rigid ring model of the tire is capable of describing the in-plane eigenmode shapes in the frequency range of 0–130 Hz. The well-known “brush model,” integrated into the tire model, is introduced to take into account the slide phenomena in the contact patch. The parameters of the model can be correlated with the physical properties of the tire so that designers can take advantage of such a correlation in the development of new tires in terms of time, cost, and performance. The technique used to determine the parameters of the model for some automobile tires include the direct measurements of some physical properties (mass, moment of inertia, stiffness) and a method of identification applied on the results from a dynamic test. The model is able to predict experimental data in terms of natural frequencies and relative dampings. Results from the application of this technique on two tires are reported.

Download Full-text

A Reliability-Based Approach to Assess Fatigue Behaviour Based on Small Incomplete Data Sets

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.44-46.871 ◽

2008 ◽

Vol 44-46 ◽

pp. 871-878 ◽

Cited By ~ 4

Author(s):

Chu Yang Luo ◽

Jun Jiang Xiong ◽

R.A. Shenoi

Keyword(s):

Incomplete Data ◽

Standard Procedure ◽

Fatigue Behaviour ◽

Fatigue Tests ◽

Small Sample ◽

Data Sets ◽

Safe Life ◽

A New Technique ◽

And Performance

This paper outlines a new technique to address the paucity of data in determining fatigue life and performance based on reliability concepts. Two new randomized models are presented for estimating the safe life and pS-N curve, by using the standard procedure for statistical analysis and dealing with small sample numbers of incomplete data. The confidence level formulations for the safe and p-S-N curve are also given. The concepts are then applied for the determination of the safe life and p-S-N curve. Two sets of fatigue tests for the safe life and p-S-N curve are conducted to validate the presented method, demonstrating the practical use of the proposed technique.

Download Full-text

Anatomic bases of a new technique of juxta-acetabular osteotomy technical principles and performance

Surgical and Radiologic Anatomy ◽

10.1007/bf01628887 ◽

1998 ◽

Vol 20 (3) ◽

pp. 153-159

Author(s):

J. Y. Lazennec ◽

N. Mora Valladares ◽

C. G. Laudet ◽

D. Barabas ◽

S. Ramare ◽

...

Keyword(s):

New Technique ◽

A New Technique ◽

And Performance ◽

Technical Principles

Download Full-text

Separating Cloud and Drizzle Radar Moments during Precipitation Onset Using Doppler Spectra

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-11-00195.1 ◽

2013 ◽

Vol 30 (8) ◽

pp. 1656-1671 ◽

Cited By ~ 48

Author(s):

Edward P. Luke ◽

Pavlos Kollias

Keyword(s):

Cloud Base ◽

Doppler Spectrum ◽

Retrieval Algorithm ◽

Cloud Droplets ◽

Gaussian Shape ◽

Model Parameterization ◽

Atmospheric Radiation Measurement ◽

Shape Property ◽

A New Technique ◽

Turbulence Parameters

Abstract The retrieval of cloud, drizzle, and turbulence parameters using radar Doppler spectra is challenged by the convolution of microphysical and dynamical influences and the overall uncertainty introduced by turbulence. A new technique that utilizes recorded radar Doppler spectra from profiling cloud radars is presented here. The technique applies to areas in clouds where drizzle is initially produced by the autoconversion process and is detected by a positive skewness in the radar Doppler spectrum. Using the Gaussian-shape property of cloud Doppler spectra, the cloud-only radar Doppler spectrum is estimated and used to separate the cloud and drizzle contributions. Once separated, the cloud spectral peak can be used to retrieve vertical air motion and eddy dissipation rates, while the drizzle peak can be used to estimate the three radar moments of the drizzle particle size distribution. The technique works for nearly 50% of spectra found near cloud top, with efficacy diminishing to roughly 15% of spectra near cloud base. The approach has been tested on a large dataset collected in the Azores during the Atmospheric Radiation Measurement Program (ARM) Mobile Facility deployment on Graciosa Island from May 2009 through December 2010. Validation of the proposed technique is achieved using the cloud base as a natural boundary between radar Doppler spectra with and without cloud droplets. The retrieval algorithm has the potential to characterize the dynamical and microphysical conditions at cloud scale during the transition from cloud to precipitation. This has significant implications for improving the understanding of drizzle onset in liquid clouds and for improving model parameterization schemes of autoconversion of cloud water into drizzle.

Download Full-text

Prediction of Packing Density of Milled Powder Based on Packing Simulation and Particle Shape Analysis

Materials Science Forum ◽

10.4028/www.scientific.net/msf.534-536.1621 ◽

2007 ◽

Vol 534-536 ◽

pp. 1621-1624

Author(s):

Yuto Amano ◽

Takashi Itoh ◽

Hoshiaki Terao ◽

Naoyuki Kanetake

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Shape Analysis ◽

Packing Density ◽

Particle Shape ◽

Milled Powder ◽

Spherical Particles ◽

Nonspherical Particles ◽

Property Control

For precise property control of sintered products, it is important to know the powder characteristics, especially the packing density of the powder. In a previous work, we developed a packing simulation program that could make a packed bed of spherical particles having particle size distribution. In order to predict the packing density of the actual powder that consisted of nonspherical particles, we combined the packing simulation with a particle shape analysis. We investigated the influence of the particle size distribution of the powder on the packing density by executing the packing simulation based on particle size distributions of the actual milled chromium powders. In addition, the influence of the particle shape of the actual powder on the packing density was quantitatively analyzed. A prediction of the packing density of the milled powder was attempted with an analytical expression between the particle shape of the powder and the packing simulation. The predicted packing densities were in good agreement with the actual data.

Download Full-text

Numerical Simulation of Particulates in Multistage Axial Compressors

Journal of Turbomachinery ◽

10.1115/1.4034982 ◽

2016 ◽

Vol 139 (3) ◽

Cited By ~ 6

Author(s):

Swati Saxena ◽

Giridhar Jothiprasad ◽

Corey Bourassa ◽

Byron Pritchard

Keyword(s):

High Pressure ◽

Axial Compressor ◽

Airborne Particulate Matter ◽

Spherical Particles ◽

Nonspherical Particles ◽

Qualitative Comparison ◽

Axial Compressors ◽

Sand Erosion ◽

High Pressure Compressor ◽

Pressure Compressor

Aircraft engines ingest airborne particulate matter, such as sand, dirt, and volcanic ash, into their core. The ingested particulate is transported by the secondary flow circuits via compressor bleeds to the high pressure turbine and may deposit resulting in turbine fouling and loss of cooling effectiveness. Prior publications focused on particulate deposition and sand erosion patterns in a single stage of a compressor or turbine. This work addresses the migration of ingested particulate through the high pressure compressor (HPC) and bleed systems. This paper describes a 3D CFD methodology for tracking particles along a multistage axial compressor and presents particulate ingestion analysis for a high pressure compressor section. The commercial CFD multiphase solver ANSYS CFX® has been used for flow and particulate simulations. Particle diameters of 20, 40, and 60 μm are analyzed. Particle trajectories and radial particulate profiles are compared for these particle diameters. The analysis demonstrates how the compressor centrifuges the particles radially toward the compressor case as they travel through the compressor; the larger diameter particles being more significantly affected. Nonspherical particles experience more drag as compared to spherical particles, and hence a qualitative comparison between spherical and nonspherical particles is shown.

Download Full-text

Fast computation of accurate sphere-cube intersection volume

Engineering Computations ◽

10.1108/ec-02-2016-0052 ◽

2017 ◽

Vol 34 (4) ◽

pp. 1204-1216 ◽

Cited By ~ 7

Author(s):

Bruce D. Jones ◽

John R. Williams

Keyword(s):

Linear Relationship ◽

Design Methodology ◽

Particle Systems ◽

Spherical Particles ◽

Immersed Boundary ◽

Computationally Efficient ◽

Content Type ◽

Linear Approach ◽

Large Numbers ◽

And Performance

Purpose Volume mapping of large spherical particles to a Cartesian grid with smaller grid elements is typically required in application of simple immersed boundary conditions in coupled engineering simulations. However, there exists no unique analytical solution to computation of the volume of intersection between spheres and cubes. The purpose of this paper is to determine a suitable solution to this problem depending on the required level of accuracy. Design/methodology/approach In this work, existing numerical techniques for computing intersection volume are reviewed and compared in terms of accuracy and performance. In addition to this, a more efficient linear relationship is proposed and included in this comparison. Findings The authors find in this work that a simple linear relationship is both acceptably accurate and more computationally efficient than the contemporary techniques. Originality/value This simple linear approach may be applied to accurately compute solutions to fluid-particle systems with very large numbers of particles.

Download Full-text

Observational and Modeling Study of Ice Hydrometeor Radar Dual-Wavelength Ratios

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-19-0018.1 ◽

2019 ◽

Vol 58 (9) ◽

pp. 2005-2017 ◽

Cited By ~ 6

Author(s):

Sergey Y. Matrosov ◽

Maximilian Maahn ◽

Gijs de Boer

Keyword(s):

Rayleigh Scattering ◽

Elevation Angle ◽

Characteristic Size ◽

Dual Wavelength ◽

Spherical Particles ◽

Nonspherical Particles ◽

Dual Frequency ◽

Weather Radars ◽

W Band ◽

Differential Reflectivity

AbstractThe influence of ice hydrometeor shape on the dual-wavelength ratio (DWR) of radar reflectivities at millimeter-wavelength frequencies is studied theoretically and on the basis of observations. Data from dual-frequency (Ka–W bands) radar show that, for vertically pointing measurements, DWR increasing trends with reflectivity Ze are very pronounced when Ka-band Ze is greater than about 0 dBZ and that DWR and Ze values are usually well correlated. This correlation is explained by strong relations between hydrometeor characteristic size and both of these radar variables. The observed DWR variability for a given level of reflectivity is as large as 8 dB, which is in part due to changes in mean hydrometeor shape as expressed in terms of the particle aspect ratio. Hydrometeors with a higher degree of nonsphericity exhibit lower DWR values when compared with quasi-spherical particles because of near-zenith reflectivity enhancements for particles outside the Rayleigh-scattering regime. When particle mass–size relations do not change significantly (e.g., for low-rime conditions), DWR can be used to differentiate between quasi-spherical and highly nonspherical hydrometeors because (for a given reflectivity value) DWR tends to increase as particles become more spherical. Another approach for differentiating among different degrees of nonsphericity for larger scatterers is based on analyzing DWR changes as a function of radar elevation angle. These changes are more pronounced for highly nonspherical particles and can exceed 10 dB. Measurements of snowfall spatiotemporally collocated with spaceborne CloudSat W-band radar and ground-based S-band operational weather radars also indicate that DWR values are generally smaller for ice hydrometeors with higher degrees of nonsphericity, which, for the same level of S-band reflectivity, exhibit greater differential reflectivity values.

Download Full-text

Performance Improvement of Wild Flower Boundary Extraction in Complex Background

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.284-287.2407 ◽

2013 ◽

Vol 284-287 ◽

pp. 2407-2410

Author(s):

Xiang Hua Li ◽

Hyo Haeng Lee ◽

Kwang Woo Chung ◽

Kwang Seok Hong

Keyword(s):

Performance Improvement ◽

Color Image ◽

Boundary Extraction ◽

Complex Background ◽

Gradient Magnitude ◽

Edge Points ◽

Color Gradient ◽

Boundary Tracing ◽

A New Technique ◽

And Performance

The performance of an automatic system for extracting flower boundaries for ten different types of wild flowers has been improved. The proposed flower boundary extraction method consists of three major procedures: the detection of four edge points, boundary tracing and performance improvement part. The flower boundary extraction part involves a new technique for automatically identifying the boundary of a flower in an image. An Intelligent Scissor algorithm is applied for boundary tracing. The color gradient magnitude and Canny edge detection are analyzed and included as the cost terms of the Intelligent Scissor algorithm. The color gradient magnitude cost term is implemented so that it can act directly on the three components of the color image. For the third procedure, we implement performance improvement. The main advantage of the proposed method was that when the program detected the wrong four edge points, using the mouse the correct positions could be clicked. The proposed method was applied to 500 photos of 10 different flowers, with 50 photos of each flower all in a complex background. The experimental results showed an extraction rate of 79.4%, which was better than before.

Download Full-text