Search results for "particle size distribution"
showing 10 items of 14 documents
On the Dependence of Cirrus Parametrizations on the Cloud Origin
2019
<p>Particle size distributions (PSDs) for cirrus clouds are important for both climate models as well as many remote sensing retrieval methods. Therefore, PSD parametrizations are required. This study presents parametrizations of Arctic cirrus PSDs. The dataset used for this purpose originates from balloon-borne measurements carried out during winter above Kiruna (Sweden), i.e. north of the Arctic circle. The observations are sorted into two types of cirrus cloud origin, either in-situ or liquid. The cloud origin describes the formation pathway of the ice particles. At temperatures below −38 °C, ice particles form in-situ from solution or ice nuclea…
The effects of different combinations of fixed and moving bed bioreactors on rainbow trout (Oncorhynchus mykiss) growth and health, water quality and…
2019
Abstract The effect of bioreactor design on nitrification efficiency has been well studied, but less is known about the overall impacts on water quality. Besides nitrification, submerged fixed bed bioreactors (FBBR) trap fine solid particles, whereas moving bed bioreactors (MBBR) grind solids, possibly increasing solids and particle accumulation in the system. In this experiment, the effects of different combinations of fixed bed and moving bed bioreactors on water quality, solids removal, particle size distribution, fish health based on histopathological changes and nitrification efficiency were studied in laboratory scale recirculating aquaculture systems (RAS) with rainbow trout (Oncorhy…
Contribution à l'étude des liaisons optiques atmosphériques : propagation, disponibilité et fiabilité.
2005
In this work we study the fog attenuation in the visible and infrared spectral band related to Free Space Optics (FSO). Based on the Mie scattering theory, fog extinction coefficients for different particle size distributions as a function of wavelength were derived. A simple analytical model allowing the prediction of atmospheric transmission for the 0.69 - 1.55 µm spectral band was developed. This model is valid for advection and convection fog and for visibility range between 50 to 1000 m. This model, implemented into software developed at FT R&D, allows the prediction of the Quality of Service of FSO links. Finally, we performed an experimental study to compare the fog effect on two FSO…
Testing the shape-similarity hypothesis between partide-size distribution and water retention for sicilian soils
2012
Application of the Arya and Paris (AP) model to estimate the soil water retention curve requires a detailed description of the particlesize distribution (PSD) but limited experimental PSD data are generally determined by the conventional sieve-hydrometer (SH) method. Detailed PSDs can be obtained by fitting a continuous model to SH data or performing measurements by the laser diffraction (LD) method. The AP model was applied to 40 Sicilian soils for which the PSD was measured by both the SH and LD methods. The scale factor was set equal to 1.38 (procedure AP1) or estimated by a logistical model with parameters gathered from literature (procedure AP2). For both SH and LD data, procedure AP2 …
Airborne measurements of dust layer properties, particle size distribution and mixing state of Saharan dust during SAMUM 2006
2009
The Saharan Mineral Dust Experiment (SAMUM) was conducted in May/June 2006 in southern Morocco. As part of SAMUM, airborne in situ measurements of the particle size distribution in the diameter range 4 nm < Dp < 100 μm were conducted. The aerosol mixing state was determined below Dp < 2.5 μm. Furthermore, the vertical structure of the dust layers was investigated with a nadir-looking high spectral resolution lidar (HSRL). The desert dust aerosol exhibited two size regimes of different mixing states: below 0.5 μm, the particles had a non-volatile core and a volatile coating; larger particles above 0.5 μm consisted of non-volatile components and contained light absorbing material. In…
Differenziazione e quantificazione dei carbonati litogenici e pedogenici di Gypsisuoli forestali attraverso l'analisi isotopica
2004
Gli autori riferiscono sui tipi e sui modelli di genesi dei carbonati dei suoli, attraverso l’uso degli isotopi del 13C. Lo studio è stato condotto in un’area dell’interno collinare argilloso siciliano, su suoli che evolvono sui depositi evaporitici della Serie Gessoso-Solfifera. Sono stati scelti cinque pedon su litotipi calcarei e non. I pedon sono stati descritti in campo e campionati secondo la sequenza degli orizzonti genetici; sui campioni di suolo sono state eseguite le seguenti analisi: tessitura, reazione, conducibilità elettrica, gesso, carbonio organico ed inorganico. Inoltre, parallelamente sono state eseguite le analisi isotopiche del carbonio organico ed inorganico. I risultat…
Inverse task for evaluation of particle size distribution of polydisperse magnetic fluids
2010
AbstractThe method of inverse task was used to analyze three different physical phenomena. The particle size distributions were reconstructed from the magnetization curve, dynamic light scattering and magnetic birefringence relaxation data. The results thus obtained for one real magnetic fluid sample are different; they characterize the physical nature of the phenomena. All three methods may be used to determine intrinsic sample properties.
Scour on alluvial bed downstream of grade-control structures
2004
This paper describes an approach for predicting local scour downstream of grade control structures. The developed analysis applies the incomplete self-similarity (ISS) theory for deducing some physically based dimensionless groups controlling the geometrical pattern of the scour profile. The scour measurements available in the literature in conjunction with numerous unpublished data allow a multiregressive calibration of the ISS relationships. The experimental sample includes different bed grain-size distributions and scales of the erosive phenomenon. The results prove that the ratio between the upstream water head and the weir height is able to explain the measurements of scour depth carri…
Particle-size distribution and associated organic matter under different cropping systems and tillage practices in a semi arid environment.
2008
The aim of this study was to evaluate the long-term impact of different management practice and tillage tools on :1) changes in soil carbon stock with different cropping systems and soil tillage managements; 2) aggregate size distribution and organic carbon concentration of each fraction; 3) organic matter composition and stability Methodology The research was carried out at the Pietranera farm, located in southern part of central Sicily (Italy) (37°32’74” N / 13°31’53” E; elevation 236 m; mean annual precipitation 481 mm; mean air temperature 19 °C) on a soil of a long term experiment. The soil is classified as a fine-clayey, calcareous, mixed, xeric Chromic Pelloxerert with a slope of 4%.…
INFLUENCE OF PARTICLE-SIZE DISTRIBUTION MEASUREMENT METHOD ON THE PREDICTION OF SOIL WATER RETENTION CURVE
2013
Application of the Arya and Paris (AP) model to estimate the soil water retention curve requires detailed particle-size distributions (PSD) that can be obtained by fitting a continuous model to traditional sieve-hydrometer (SH) data or using the laser diffraction (LD) method. The AP model was applied to 40 Sicilian soils for which PSD was measured by both SH and LD methods. The scale factor was set equal to 1.38 (procedure AP1) or estimated by a logistic model with parameters gathered from literature (procedure AP2). To simplify application of the AP model, a relationship for estimating a soil-specific value from clay content was developed (procedure OPT). For both SH and LD data, proce…