Effective Particle Diameter Research Articles

Dust aerosol effects on cirrus and altocumulus clouds in Northwest China

Dust aerosol effects on the properties of cirrus and altocumulus cloud in Northwest China were studied for the period March–May 2007 by using the satellite data of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), Aqua, and CloudSat. Dusty clouds were defined as those mixed with dust aerosols or existing in dust aerosol conditions, while pure clouds were those in a dust-free environment. For dusty altocumulus clouds, the mean values of cloud optical depth (OPD), cloud liquid water path (LWP), cloud ice water path (IWP), cloud effective particle radius (Re), and cloud effective particle diameter (D e) were 6.40, 40.23 g m-2, 100.70 g m-2, 8.76 μm, and 40.72 μm, respectively. For pure altocumulus clouds, the corresponding mean values were 9.28, 76.70 g m-2, 128.75 g m-2, 14.03 μm, and 48.92 μm, respectively. These results show a significant decrease of OPD, LWP, IWP, R e, and D e of approximately 31%, 48%, 22%, 38%, and 17% because of the effects of dust aerosols. Moreover, the effects of dust aerosols on liquid-phase altocumulus clouds were greater than on ice-phase altocumulus clouds. Regarding dusty cirrus clouds, the mean values of OPD, IWP, and D e were 5.11, 137.53 g m-2, and 60.44 μm, respectively. In contrast, the mean values were 6.69, 156.17 g m-2, and 66.63 μm, respectively, for pure cirrus clouds, with a 24% decrease in OPD, a 12% decrease in IWP, and a 9% decrease in D e. These results indicate that dust aerosols can significantly change cloud properties, leading to a reduction of OPD, LWP, and effective particle size for both altocumulus and cirrus clouds in Northwest China.

Preparation of PEC's based on chitosan and NaPMA

Abstract Polyelectrolyte complex (PEC) nanoparticles were prepared using chitosan and sodium polymethacrylate solubilized in 2% acetic acid. General structural characterization was carried out using FTIR spectroscopy, TGA, and XRD. The mechanism of complex formation was investigated using turbidimetry, conductometry, viscometry, zeta potential measurements, and dynamic light scattering, as a function of carboxylate to aminium molar ratio. One of the main features of the resultant PECs was a decrease of chitosan-related crystallinity; on the other hand, thermal stability increased. A drastic increase in turbidity characterized the occurrence of solid, insoluble nanoparticles at a carboxyl/aminium molar ratio of ca. 0.7–0.8. At the same range, viscosity decrease was lower and conductivity increase was higher. All these changes were correlated to a less evident decrease in zeta potential and a drastic decrease in particle effective diameter, using a a proposed mechanism of complex formation based on the decrease of macromolecular dimensions of soluble polyelectrolyte complex clusters, followed by phase segregation.

Pressure drops of single/two-phase flows through porous beds with multi-sizes spheres and sands particles

This paper reports an experimental research of single and two-phase gas/liquid flow in packed porous beds composed of multi-sizes spheres and irregular particles. A test facility named DEBECO-LT is designed and constructed to investigate the friction laws of adiabatic single and two-phase flows in a porous bed. The results show that the effective diameter of multi-sizes non-spherical or irregular particles bed can be derived on the basis of bed consisted of spheres as long as they have a wide range of grain sizes and the similar size distribution. Given the effective particle diameter obtained from single-phase flow through the packed bed with multi-size spheres or irregular particles, the pressure drop of two-phase flow through the bed can be predicted by the Reed model. The experimental data provide insights for the flow characteristic of porous bed, as well as high-quality data for validation of the coolability analysis models and codes.

Extended law of corresponding states for protein solutions.

The so-called extended law of corresponding states, as proposed by Noro and Frenkel [J. Chem. Phys. 113, 2941 (2000)], involves a mapping of the phase behaviors of systems with short-range attractive interactions. While it has already extensively been applied to various model potentials, here we test its applicability to protein solutions with their complex interactions. We successfully map their experimentally determined metastable gas-liquid binodals, as available in the literature, to the binodals of short-range square-well fluids, as determined by previous as well as new Monte Carlo simulations. This is achieved by representing the binodals as a function of the temperature scaled with the critical temperature (or as a function of the reduced second virial coefficient) and the concentration scaled by the cube of an effective particle diameter, where the scalings take into account the attractive and repulsive contributions to the interaction potential, respectively. The scaled binodals of the protein solutions coincide with simulation data of the adhesive hard-sphere fluid. Furthermore, once the repulsive contributions are taken into account by the effective particle diameter, the temperature dependence of the reduced second virial coefficients follows a master curve that corresponds to a linear temperature dependence of the depth of the square-well potential. We moreover demonstrate that, based on this approach and cloud-point measurements only, second virial coefficients can be estimated, which we show to agree with values determined by light scattering or by Derjaguin-Landau-Verwey-Overbeek (DLVO)-based calculations.

An Improved Theoretical Model of Cigarette Smoke Filtration across Mono-Segment Cellulose Acetate Filters

Summary An improved theoretical model was presented to predict the filtration efficiency of cigarette filters. Filtration equations of single fibers considering the interference of neighboring fibers were applied in the model. Cellulose acetate fibers in cigarette filters were approximated as cylinders. The fiber size was adjusted by its size projected on the flow field. The solid fraction of fibers in cigarette filters was recalculated using the size of the virtual cylinders. The varying flow velocity during smoking was taken into account when calculating the filtration efficiency. The effective hydrodynamic particle diameter of cigarette smoke was estimated to be 0.44 μm by the difference of filtration efficiencies under ISO and Health Canada Intense (HCI) smoking regimes. Filtration contributions due to diffusion, interception and inertial impaction were 62%, 32% and 6%, respectively, at a flow velocity of 0.38 m/s for particles of 0.44 μm diameter. The effect of inertial impaction was insignificant but not negligible under ISO smoking regime. The measured and predicted efficiencies of two cigarette samples were compared and satisfactory agreement was obtained. [Beitr. Tabakforsch. Int. 26 (2015) 232-240]

A novel liquid bridge model for estimating SWCC and permeability of granular material

As traditional liquid bridge model based on Yang–Laplace theory fails to model behaviors of unsaturated granular materials when liquid bridges fuse with each other in funicular and capillary regimes, a method called “Redistribution of Air Volume and Reduction of Liquid Bridge Force” is proposed, and incorporated into the original discrete element method to resolve this issue. Both soil water characteristic curve and suction stress characteristic curve are worked out by the modified discrete element method, the results of which coincide with theoretical solutions for simple cubic packing and tetrahedral packing of granular materials. Furthermore, parameter study shows that soil water characteristic curve depends on effective particle diameter, particle size distribution and packing density. Typical soil water characteristic curves of sand and silt are obtained using the modified method, with a trend similar to that of experiment qualitatively. With the help of Mualem model and Kozeny–Carman equation, permeability is also predicated for granular materials. In particular, the air entry value coincides with or close to those of typical sand and silt in magnitude. Finally, a case study of SWCC prediction for sandy soil is implemented with acceptable results. We may conclude that the modified discrete element method is capable of predicting hydraulic properties of granular materials qualitatively and semi-quantitatively.

Investigating the Ice Water Path in Convective Cloud Life Cycles to Improve Passive Microwave Rainfall Retrievals

Abstract This study focuses on the possible relationship between ice water path (IWP) retrievals using high-frequency channels (89 and 150 GHz) from the Advanced Microwave Sounding Unit-B and Moisture Humidity Sounder sensors (NOAA-16–NOAA-19) and the life cycle stage of convective clouds. In the first part of this study, the relationship between IWP and the cloud area expansion rate is analyzed using the 235-K isotherm from Geostationary Operational Environmental Satellite-12 (GOES-12) thermal infrared images (10.7 μm). Next, the relationships between cloud convective fraction, rain rates (from ground radar), and cloud life cycle are analyzed. The selected area and time period coincide with the research activities of the Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the Global Precipitation Measurement (CHUVA)–Geostationary Lightning Mapper (GLM) project at São José dos Campos, Brazil. The results show that 84% of precipitating clouds contain ice, according to the Microwave Surface and Precipitation Products System (MSPPS) algorithm. Convective systems in the intensifying stage (when the area is expanding and the minimum temperature is decreasing) tend to have larger IWPs than systems in the dissipating stage. Larger rain rates and convective fractions are also observed from radar retrievals in the early stage of convection compared with mature systems. Hydrometeor retrieval data from polarimetric X-band radar suggest that particle effective diameter De and IWP patterns inferred with the MSPPS algorithm could be used to determine the life cycle stage of a given convective system. Using this information, a new set of equations is evaluated for rainfall retrievals using De and IWP from the current retrieval algorithm. This new approach outperforms the current algorithm in the studied region.

Arsenic Removal by Nanoscale Magnetite in Guanajuato, Mexico

Increasingly, cities in Latin America are recognizing the importance of drinking water quality on public health. A water assessment of Guanajuato, Mexico, and surrounding areas indicated naturally occurring arsenic in some wells above the Mexican drinking water standard of 25 μg/L and the World Health Organization recommendation of 10 μg/L. This initiated a collaborative effort with the city to evaluate a new arsenic removal method using high surface area magnetite sorbents. Nanoscale (20 nm) magnetite particles, previously shown to effectively adsorb arsenic in batch systems, were packed in sand columns to create a continuous treatment process. Design and operating variables were evaluated to confirm that magnetite-to-sand ratio and residence time most significantly affected arsenic breakthrough profiles. Subsequently, a pilot column with 456 g (ca. $2.50 USD) of a commercially available, food-grade magnetite (98 nm effective particle diameter) from a pigment manufacturer demonstrated removal of the equivalent arsenic contained in 1,360 L of Guanajuato groundwater. Although pH reduction dramatically improved arsenic adsorption in batch isotherms, no improvement in arsenic removal efficiency was observed when applied to pilot-scale, field columns in Guanajuato. Interference effects (e.g., from background silica) and changes to surface species over time may impact adsorption differently in column versus batch systems. Overall, this work represents one of the first pilot studies of a nanotechnology-enabled water treatment system, and it demonstrates the potential and additional challenges for taking nanoscale magnetite or other highly researched nanomaterials into a complex full-scale setting.

Density–Pressure Dependence and Density Distribution During Powder Pressing

The effect of applied load on density–pressure dependence as well as density distribution under axial pressing of powders in closed dies is analyzed. The continuity hypothesis is used for the analysis. The notion of a representative element is introduced. It is established that the size of this element is related to the effective diameter of powder particles. The sensitivity of density–pressure dependence and density distribution to pressing conditions is explained. Some features of axial pressing with a rotating punch are pointed out. The personal contribution of I. D. Radomyselskii to the formulation and solution of basic problems of powder pressing theory is emphasized.

Considering polarization in MODIS-based cloud property retrievals by using a vector radiative transfer code

In this study, a full-vector, adding–doubling radiative transfer model is used to investigate the influence of the polarization state on cloud property retrievals from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations. Two sets of lookup tables (LUTs) are developed for the retrieval purposes, both of which provide water cloud and ice cloud reflectivity functions at two wavelengths in various sun-satellite viewing geometries. However, only one of the LUTs considers polarization. The MODIS reflectivity observations at 0.65μm (band 1) and 2.13μm (band 7) are used to infer the cloud optical thickness and particle effective diameter, respectively. Results indicate that the retrievals for both water cloud and ice cloud show considerable sensitivity to polarization. The retrieved water and ice cloud effective diameter and optical thickness differences can vary by as much as ±15% due to polarization state considerations. In particular, the polarization state has more influence on completely smooth ice particles than on severely roughened ice particles.

Simulation for Fine Sediment Flocculating Settlement in Flowing Water and Its Influencing Factors

The aim of this study is to simulate the growth process of fine Sediment flocculation fractal, which based on DLCA and three graphics technology. With the simulation, we analyze the effects of particle effective collision probability, initial concentration and particle diameter on sedimentation distance and distribution. The flow fractal structure was analyzed by graphic technology. Researches in this study have some theoretical and practical value on the control and treatment of Yellow River high turbidity flow.

Characterizing the effective density and primary particle diameter of airborne nanoparticles produced by spark discharge using mobility and mass measurements (tandem DMA/APM)

Nanoparticles are increasingly used in a wide variety of industries. As yet, their health effects are incompletely characterized. Effective density is among the key characteristics of airborne nanoparticles due to its role in particle deposition in the human respiratory tract and in the conversion of number distributions to mass distributions. Because it cannot be measured directly, different methods have been developed to accede to this parameter. The approach chosen in this study is based on the tandem measurement of airborne nanoparticles electrical mobility and mass (tandem differential mobility analyzer/aerosol particle mass analyzer), which major advantage lies in the absence of hypothesis contrary to the tandem differential mobility analyzer/electrical low pressure impactor (DMA/ELPI). The methodology was first applied to spherical model particles to validate the associated data treatment and protocol. In particular, the influence of APM rotational velocity and airflow rate were investigated with regards to the separation of multiply charged particles and electrometer signal. It emerged from experimental data that a compromise between separation efficiency and detection limit shall be found, depending on the nanoparticles to characterize. Accounting for their wide use in different domains, airborne nanoparticles of constantan®, copper, graphite, iron, silver and titanium, produced by spark discharge appear to be representative of ultrafine particles stemming from different industrial processes. In addition to their effective density, the mass-mobility exponents and primary particle diameters were determined for these particles, and found to agree well with published data.

A kriging approach based on Aitchison geometry for the characterization of particle-size curves in heterogeneous aquifers

We consider the problem of predicting the spatial field of particle-size curves (PSCs) from a sample observed at a finite set of locations within an alluvial aquifer near the city of Tübingen, Germany. We interpret PSCs as cumulative distribution functions and their derivatives as probability density functions. We thus (a) embed the available data into an infinite-dimensional Hilbert Space of compositional functions endowed with the Aitchison geometry and (b) develop new geostatistical methods for the analysis of spatially dependent functional compositional data. This approach enables one to provide predictions at unsampled locations for these types of data, which are commonly available in hydrogeological applications, together with a quantification of the associated uncertainty. The proposed functional compositional kriging (FCK) predictor is tested on a one-dimensional application relying on a set of 60 PSCs collected along a 5-m deep borehole at the test site. The quality of FCK predictions of PSCs is evaluated through leave-one-out cross-validation on the available data, smoothed by means of Bernstein Polynomials. A comparison of estimates of hydraulic conductivity obtained via our FCK approach against those rendered by classical kriging of effective particle diameters (i.e., quantiles of the PSCs) is provided. Unlike traditional approaches, our method fully exploits the functional form of PSCs and enables one to project the complete information content embedded in the PSC to unsampled locations in the system.

Impacts of mineral dust on ice clouds in tropical deep convection systems

Multi-platform and multi-sensor observations are used to study the impacts of mineral dust on ice clouds of tropical deep convection systems based on one massive Sahara dust event. The comparisons of cloud properties between dust-laden and dust-free conditions support the hypothesis that the presence of large concentrations of mineral dust produces more ice particles at warmer temperature through heterogeneous nucleation processes. Water vapor competition limits ice particles' growth and results in relatively small sizes of ice particles and a narrow distribution of effective particle diameter in non-precipitating ice clouds, particularly at upper layer with temperatures colder than −40 to −50°C. On the other hand, precipitating ice clouds with sufficient water vapor supply have greater ice water paths under dust-laden conditions than under dust-free conditions. The results also suggest that mineral dusts may invigorate the convection and enhance water vapor supply in deep convective precipitating clouds, lifting ice particles to higher altitudes. Additional study illustrates that the observed microphysical changes of ice clouds in the deep convection systems are not simply due to the differences of large-scale dynamics and thermodynamics.

Evaluation of Dis-Lub-Tout, a new co-processed tabletting excipient I. Study of physicochemical properties

Dis-Lub-Tout, is a new excipient co-processed from re-generated cellulose, RC, and olive oil, OL, to act as a lubricant and disintegrant in tablets and capsules formulations. The new excipient was off-white, very fine, cohesive, greasy to the touch, readily adheres to the skin and having the characteristic OL odour. The effective mean particle diameter of the excipient was 3 μm. Dis-Lub-Tout exhibited moisture sorption isotherm more or less equal to that exhibited by re-generated cellulose lubricated with equivalent concentration of magnesium stearate. The thermo-degradation of OL in Dis-Lub-Tout followed the first order mechanism with rate constants amenable to Arrhenius treatment. The degradation under humid condition was faster and also followed the first order mechanism with rate constants depending on the amount of the water adsorbed by the tested sample. The co-processed material developed a faint rancidity odour after 12 months shelf storage.

Retrieval of cirrus properties by Sun photometry: A new perspective on an old issue

Cirrus clouds are important modulators of the Earth radiation budget and continue to be one of the most uncertain components in weather and climate modeling. Sun photometers are widely accepted as one of the most accurate platforms for measuring clear sky aerosol optical depth (AOD). However, interpretation of their measurements is ambiguous in the presence of cirrus. Derivation of a valid AOD under cirrus conditions was focused previously on correction factors, rather than on derivation of cirrus cloud optical thickness (COT). In the present work, we propose a new approach that uses the total measured irradiance to derive cirrus COT and ice particle effective diameter (Deff). For this approach, we generate lookup tables (LUTs) of total transmittance for the Sun photometer field of view (FOV) due to the direct and scattered irradiance over the spectral range of 400–2200 nm, for a range of cirrus COT (0–4), and a range of ice cloud effective diameters (10–120 µm) by using explicit cirrus optical property models for (a) cirrus only and (b) a two‐component model including cirrus and aerosols. The new approach is tested on two cases (airborne and ground‐based) using measured transmittances from the 14‐channel NASA Ames Airborne Tracking Sun photometer. We find that relative uncertainties in COT are much smaller than those for Deff. This study shows that for optically thin cirrus cases (COT < 1.0), the aerosol layer between the instrument and the cloud plays an important role, especially in derivation of Deff. Additionally, the choice of the cirrus model may introduce large differences in derived Deff.

Pulverised wood combustion in a vertical furnace: Experimental and computational analyses

Experimental and numerical investigations of pulverised wood flames in a laboratory vertical furnace are carried out. The aims are to study the fundamental structures of pulverised wood flames, to identify the basic reasons that cause the emissions of unburned volatiles and particles, and to provide experimental data for model validations. Three different fuel particles are investigated; the particle effective diameter ranges from 0.02mm to 1.2mm and the length is about 5 times the diameter. Rather high emission of unburned hydrocarbons and carbon monoxide are recorded in the experiments. It is found that pulverised wood flames have similarities to gas premixed flames; distinct zones are found in pulverised wood flames – preheat zone, drying and devolatilization zone, oxidation zone and post-flame zone. The mechanism of heat transfer to the preheat zone of pulverised wood flames is rather different from the gas flames. The former is by virtue of radiation from the walls and the flames to the fuel particles; the latter is by diffusion (molecular and turbulent diffusion) from the reaction zone. This makes the emissions from pulverised wood flames rather sensitive to the particle size and combustor/burner configurations. An important feature of pulverised wood flames found in the experiments is the effect of particle devolatilization on the dispersion of the particles. A model is developed to account for this dispersion effect.

Morphology, Structure, Thermal Stability, XR-Diffraction, and Infrared Study of Hexadecyltrimethylammonium Bromide–Modified Smectite

We characterized the interlayer structure and morphology of modified natural clays. Organoclay-based materials are increasingly used for multiple applications. We modified a purified Na-bentonite using cation exchange with hexadecyltrimethyl ammonium bromide (HDTMA) and characterized it using; UV spectroscopy, X-ray diffraction, photoacoustic FTIR spectroscopy (PA-FTIR), thermogravimetric analysis (TGA) techniques, laser scattering distribution (LSD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The adsorption of HDTMA on interlayer sites of Na-smectite fraction is nearly total until an adsorption equivalent to 1.85 times the cation exchange capacity (CEC) of the clay. The formation of the HDTMA-smectite changes the properties of the clay from hydrophilic to hydrophobic. The XRD patterns show an increase in the basal spacings. TGA characterization and analysis were shown to be useful to estimate the amount of surfactant within the organoclay. LSD analyses have shown a decrease of the effective particle diameter with increasing sonication times. AFM images showed that these Na-smectite surfaces appeared foliated with irregular aggregate structures at high HDTMA loading. The present study shows that not only the basal spacing but the morphology and the particle size of the organoclay strongly depend on the packing density of surfactant within the smectite interlayer space.

Model and simulation predictions of the thermal conductivity of compact random nanoparticle composites

The lattice thermal conductivity of compact random nanoparticle composites was investigated numerically as well as theoretically. By taking advantage of the three-dimensional Vorogoni diagrams, we were able to generate realistic numerical models of the composites. The phonon motion was then simulated in use of a Monte-Carlo simulator which employed an unstructured grid system (tetrahedron cells) and was developed under the single relaxation time approximation and the grey medium approximation. On the other hand, a new effective medium approximation (EMA) model was proposed in the present work to predict the thermal conductivity of nanoparticle composites which particles are all made of a same material type. This EMA model was next combined with the EMA model proposed by Liang and Ji (2000) for three bond percolation systems to predict the thermal conductivity of nanoparticle composites of two material types. It was found that with an effective particle diameter characterizing either the average particle volume or the average particle surface area, the model predictions agree excellently with the Monte-Carlo simulation results and match well with the measurements of nanostructured bulk alloys.

Properties of linear contrails in the Northern Hemisphere derived from 2006 Aqua MODIS observations

Understanding the role of contrails in the Earth's radiation budget requires an accurate characterization of their macrophysical and microphysical properties, such as cloud top temperature, optical depth, and effective particle size. These properties are derived from 2006 MODerate‐resolution Imaging Spectroradiometer data over the Northern Hemisphere using a bi‐spectral, infrared‐only retrieval technique. Contrail temperature is estimated using a quadratic relationship of flight track pressure with latitude. The results reveal distinct seasonal trends in contrail microphysical properties, with slightly greater mean optical depths and slightly smaller particle sizes during summer. The average contrail optical depth and particle effective diameter are 0.216 and 35.7 µm, respectively. Although fewer contrails occurred at night, there are no appreciable diurnal differences in their retrieved properties. These results should help to fill the gap in our knowledge of contrail properties and will be valuable for model validation.