Fraction Of Large Particles Research Articles

Nonlinear resonance in an acoustic system with a coagulating gas suspension

The occurrence of resonance in an acoustic system as a result of a change of the dispersion of a gas suspension filling a resonator with fixed external excitation parameters was studied. The dynamics of the medium is described by a system of equations of motion of a multi-velocity multi temperature continuum taking into account pulse and energy exchange between the carrier phase and the disperse fractions. Coagulation of different particle fractions is simulated by Smolukhovskii’s Lagrangian model, which takes into account pair collisions. Resonance occurs as a result of the resonance frequency of the system approaching a fixed external excitation frequency as a result of a change in the dispersion of the gas suspension during coagulation initiated by the addition of a small amount of the large particle fraction to the finely dispersed gas suspension. As a result of calculations, an estimate for the time of the change in dispersion of the system and the generation of resonance oscillations were obtained.

Effect of pre-treatment and drying method on physico-chemical properties and dry fractionation behaviour of mealworm larvae (Tenebrio molitor L.)

Edible insects have emerged as an alternative source for feed and food. Fractionation is considered as a promising strategy to produce standardised insect-based intermediates to augment industrial applicability and consumer acceptance. So far, mainly wet fractionation techniques were studied to separate insect components and concentrate protein. This study investigated a dry fractionation approach to yield protein-enriched and differently composed fractions of mealworm larvae (Tenebrio molitor). The influence of post-harvest procedures including different pre-treatments (blanching, freezing, etc.), drying methods (oven drying, fluidized bed drying, freeze-drying, etc.), and defatting on physico-chemical properties of the larvae were studied. Furthermore, the impact of pre-processing on disintegration of larvae during roller milling was investigated via sieve classification. Applied post-harvest process chain significantly affected the colour, dimensions, apparent density, and hardness of dried larvae with an impact on fractionation behaviour and characteristics of the obtained fractions. Drying at elevated temperatures caused pronounced darkening and shrinkage due to browning reactions and tissue collapse. Mechanical properties were affected as well leading to heterogeneous particle size distributions after milling and sieving. A large fraction of particles <500 µm was determined for samples exhibiting low mechanical hardness such as freeze-dried and defatted larvae. Significant differences in macro-nutrient composition of the sieving fractions were found deviating in chitin (3.6–16.1%db), protein (52.5–58.2%db) and fat (21.4–26.6%db) content. Highest protein recovery of max 72% was determined in the particle size fraction 500–1000 µm. Concluding, these results provide insights into physico-chemical characteristics of mealworms affected by pre-treatment and drying. The potential of dry fractionation techniques for protein enrichment and delivery of a variety of differently composed mealworm fractions was demonstrated and may provide an interesting potential to optimize water and energy consumption during insect fractionation.

Optimal Run Strategies in Monte Carlo Iterated Fission Source Simulations

The method of successive generations used in Monte Carlo simulations of nuclear reactor models is known to suffer from intergenerational correlation between the spatial locations of fission sites. One consequence of the spatial correlation is that the convergence rate of the variance of the mean for a tally becomes worse than O(N–1). In this work, we consider how the true variance can be minimized given a total amount of work available as a function of the number of source particles per generation, the number of active/discarded generations, and the number of independent simulations. We demonstrate through both analysis and simulation that under certain conditions the solution time for highly correlated reactor problems may be significantly reduced either by running an ensemble of multiple independent simulations or simply by increasing the generation size to the extent that it is practical. However, if too many simulations or too large a generation size is used, the large fraction of source particles discarded can result in an increase in variance. We also show that there is a strong incentive to reduce the number of generations discarded through some source convergence acceleration technique. Furthermore, we discuss the efficient execution of large simulations on a parallel computer; we argue that several practical considerations favor using an ensemble of independent simulations over a single simulation with very large generation size.

Internally mixed black carbon in the Indo-Gangetic Plain and its effect on absorption enhancement

We present the systematic analysis of individual black carbon (BC) mixing state and its impact on radiative forcing from an urban Indian city, Kanpur, located in Indo-Gangetic Plain (IGP). Simultaneous measurements using Single Particle Soot Photometer (SP2), Photo-Acoustic Soot Spectrometer (PASS-3) and High-Resolution Time-of-Flight Aerosol Mass Spectrometer (AMS) were conducted from 8 January 2015 to 28 February 2015 at Kanpur. BC mass and number concentrations varied between 0.7 and 17μg/m3 and 277–5866#/cm3 with a mean of 4.06μg/m3 and 1314#/cm3, respectively. The diurnal variation of BC mass concentration showed a traffic hour peak during both the morning and late night. The mean fraction of “thickly coated BC” particles (fTCBC) was found to be 61.6%, indicating that a large fraction of BC particles was internally mixed. The fTCBC increased after sunrise with a peak at about noontime, indicating that the formation of secondary organic aerosol under active photochemistry can enhance organic coating on a core of black carbon. High-resolution positive matrix factorization (HR-PMF) factors showed distinct characteristics with fTCBC. While primary organic aerosols like cooking organic aerosols (COA) and biomass burning organic aerosols (BBOA) were negatively correlated with fTCBC (r=−0.78 and −0.51, respectively), aged low volatile oxygenated organic aerosol (LVOOA) was forming a coating over BC (r=0.6). Similar positive correlation of fTCBC with inorganic species like ammonium (r=0.58) and nitrate (r=0.47) further suggested that BC appears to be largely coated with LVOOA, ammonium, and nitrate. A positive correlation between the fTCBC and the mass absorption cross-section at 781nm (MAC781) was also observed (r=0.58). Our results suggest that the observed fTCBC could amplify the MAC781 approximately by a factor of 1.8, which may catalyze the positive radiative forcing in the IGP.

Comparative selective retention of particle size classes in the gastrointestinal tract of ponies and goats.

There is a discrepancy in the literature on potential digesta separation mechanisms in horses, with both a selective retention of fine and of large particles postulated in different publications. To assess the net effect of such mechanisms, we fed ponies on a hay-only diet a pulse dose of whole (unchopped) marked hay together with a solute marker, collected faeces on a regular basis, measured marker concentrations in whole faeces and in their large (2.0-16mm), medium (0.5-1.0mm) and small (0.063-0.25mm) particle fraction, and calculated the corresponding mean retention times (MRTs). For comparison, the same experiment was performed in goats. In goats, as expected, MRTsolute (35hr) was significantly shorter than MRTparticle (51hr); only a very small fraction of particle marker was excreted as large particles (2%); and the MRT of these large particles was significantly shorter than that of small particles (with a relevant difference of 8.6hr), indicating that those few large particles that escape the rumen do so mostly soon after ingestion. In ponies, MRTsolute (24hr) did not differ from MRTparticle (24hr); a higher fraction of particle marker was excreted as large particles (5%); and the MRT of these large particles was longer than that of small particles (but with a non-relevant difference of less than 1hr). These results indicate that no relevant net separation of digesta phases occurs in horses and that selective particle retention mechanisms in the large intestine are unlikely to represent important characteristics of the horse's digestive physiology.

Fabrication and Test of Model Superconducting Inflector for g-2 at FNAL

The new FNAL g-2 experiment is based on the muon storage ring previously used at BNL. The 1.45 T dipole magnetic field in the storage ring is required to have very high (1 ppm) homogeneity. The muon beam injected into the ring must be transported through the magnet yoke and the main superconducting coil cryostat with minimal distortions. The old inflector magnet shielded the main dipole fringe field inside the muon transport beam pipe, with an outer NbTi superconducting screen, and did not disturb the field in the area of circulating beam. Nevertheless, this magnet had coils with closed ends in which a large fraction of muon beam particles were lost. A new magnet is envisioned utilizing the same cross section as the original with open ends for improved beam transport. A model magnet has been wound utilizing 3d printed parts to verify the magnetic behavior of the magnet at room temperature and validate winding of the complicated geometry required for the magnet ends. Finally, room temperature magnetic measurements have been performed and confirm the magnetic design

Magnetic properties of nanoparticle compacts with controlled broadening of the particle size distribution

Binary random compacts with different proportions of small (volume V) and large (volume 2V) bare maghemite nanoparticles (NPs) are used to investigate the effect of controllably broadening the particle size distribution on the magnetic properties of magnetic NP assemblies with strong dipolar interaction. A series of eight random mixtures of highly uniform 9.0 and 11.5 nm diameter maghemite particles prepared by thermal decomposition are studied. In spite of severely broadened size distributions in the mixed samples, well defined superspin glass transition temperatures are observed across the series, their values increasing linearly with the weight fraction of large particles.

Turbulent channel flow of a dense binary mixture of rigid particles

We study turbulent channel flow of a binary mixture of finite-sized neutrally buoyant rigid particles by means of interface-resolved direct numerical simulations. We fix the bulk Reynolds number and total solid volume fraction, $Re_{b}=5600$ and $\unicode[STIX]{x1D6F7}=20\,\%$, and vary the relative fraction of small and large particles. The binary mixture consists of particles of two different sizes, $2h/d_{l}=20$ and $2h/d_{s}=30$ where $h$ is the half-channel height and $d_{l}$ and $d_{s}$ the diameters of the large and small particles. While the particulate flow statistics exhibit a significant alteration of the mean velocity profile and turbulent fluctuations with respect to the unladen flow, the differences between the mono-disperse and bi-disperse cases are small. However, we observe a clear segregation of small particles at the wall in binary mixtures, which affects the dynamics of the near-wall region and thus the overall drag. This results in a higher drag in suspensions with a larger number of large particles. As regards bi-disperse effects on the particle dynamics, a non-monotonic variation of the particle dispersion in the spanwise (homogeneous) direction is observed when increasing the percentage of small/large particles. Finally, we note that particles of the same size tend to cluster more at contact whereas the dynamics of the large particles gives the highest collision kernels due to a higher approaching speed.

Fractionation of distillers dried grains with solubles (DDGS) by combination of sieving and aspiration

Distiller’s dried grains with solubles (DDGS) is a coproduct of the corn-based ethanol industry and it is a good resource of protein and oil for animal feeds. High protein and oil content DDGS is desired because of its high nutrition and economic values. Physical separation is an easy approach to increase oil and fat content based on profiles of components. Protein and oil rich DDGS tends to exist in the finer particle; fibers rich DDGS is observed in large particle fraction. A primary sieving connected with aspiration fraction is used to condense protein and oil contents for DDGS. Particle size, air flowrate and different fractions derived by aspiration are independent variables. The proper combination and interaction of variables for protein and oil separation are higher flowrate, smaller particle sizes, and the heavy fraction. And, the best efficiency for protein and oil separation reaches about 29.7% and 68.15% respectively. For fiber separation, a mild condition results in higher fiber content approximately 7%. Additionally, the relationship between nutrient separation and independent variables can be expressed by a linear model. The combination of primary sieving and aspiration with specific air flowrate used in fractionation process can increase value to the corn-based ethanol industry.

ADVANCEMENTS IN DRY POWDER INHALER

The dry powder inhaler (DPI) has become widely known as a very attractive platform for drug delivery. DPIs are being used for the treatment of asthma and chronic obstructive pulmonary disease by many patients. There are over 20 devices presently in the DPI market. DPIs are preferred over nebulizers and pressurized metered dose inhalers. However, some of the challenges of DPI are dependence on inspiratory flow (unsuitable for young children, elderly people), systemic absorption due to deposition of drug in deep lung (unsuitable for local diseases treatment), and increase in upper airway deposition of a large fraction of coarse particles. Hence, there is a need to address these unmet issues. The interpatient variation can be minimized by developing devices independent of patient’s inspiratory flow rate or active based powder mechanism. This article reviews DPI devices currently available, advantages of newly developed devices, and formulation technologies. The platform technologies are developed to improve aerosolization and dispersion from the device and decrease the patient related factors. The DPI delivery system has been expanded to treatment of non-respiratory diseases such as migraine and diabetes. The development of innovative DPI device and formulation technologies for delivering therapeutic proteins such as insulin has been accelerated to overcome the problems associated with conventional insulin therapy.Keywords: Dry powder inhaler, Inspiratory flow rate, Insulin, Platform technologies.

Online single particle analysis of ice particle residuals from mountain-top mixed-phase clouds using laboratory derived particle type assignment

Abstract. In situ single particle analysis of ice particle residuals (IPRs) and out-of-cloud aerosol particles was conducted by means of laser ablation mass spectrometry during the intensive INUIT-JFJ/CLACE campaign at the high alpine research station Jungfraujoch (3580 m a.s.l.) in January–February 2013. During the 4-week campaign more than 70 000 out-of-cloud aerosol particles and 595 IPRs were analyzed covering a particle size diameter range from 100 nm to 3 µm. The IPRs were sampled during 273 h while the station was covered by mixed-phase clouds at ambient temperatures between −27 and −6 °C. The identification of particle types is based on laboratory studies of different types of biological, mineral and anthropogenic aerosol particles. The outcome of these laboratory studies was characteristic marker peaks for each investigated particle type. These marker peaks were applied to the field data. In the sampled IPRs we identified a larger number fraction of primary aerosol particles, like soil dust (13 ± 5 %) and minerals (11 ± 5 %), in comparison to out-of-cloud aerosol particles (2.4 ± 0.4 and 0.4 ± 0.1 %, respectively). Additionally, anthropogenic aerosol particles, such as particles from industrial emissions and lead-containing particles, were found to be more abundant in the IPRs than in the out-of-cloud aerosol. In the out-of-cloud aerosol we identified a large fraction of aged particles (31 ± 5 %), including organic material and secondary inorganics, whereas this particle type was much less abundant (2.7 ± 1.3 %) in the IPRs. In a selected subset of the data where a direct comparison between out-of-cloud aerosol particles and IPRs in air masses with similar origin was possible, a pronounced enhancement of biological particles was found in the IPRs.

Comparison of Aerosol Hygroscopcity, Volatility, and Chemical Composition between a Suburban Site in the Pearl River Delta Region and a Marine Site in Okinawa

ABSTRACTA suite of advanced instruments were employed to measure aerosol hygroscopicity, volatility and chemical composition at a suburban site in the Pearl River Delta (PRD) Region and at a marine site in Okinawa, respectively. The results showed that the particle number concentration in PRD is approximately ten times higher than that in Okinawa. Organics contributes about one half of the total NR-PM1 concentration in PRD, while sulfate is the dominant component (about 60%) in Okinawa. Diurnal variation of the chemical species demonstrated that the site in PRD was affected by traffic-related sources and industrial emissions, while the one in Okinawa is mainly affected by regional emissions. The V-TDMA measurements showed that a large fraction (20–45%) of particles in Okinawa volatilized at about 200°C and nearly all particles volatilized at about 300°C, indicating that the particles were almost volatile in Okinawa. In contrast, a fraction (15–21%) of particles in PRD did not evaporate even when heated to about 300°C, implying that these particles might contain black carbon or low-volatile organics. For 40–200 nm particles in Okinawa, the hygroscopicity parameter κ is around 0.5, significantly higher than that of PRD particles (κ ≈ 0.26). Particles tend to have bimodal distribution in PRD and unimodal in Okinawa, indicating that the former is externally mixed while the latter is internally mixed.

Aircraft Measurements of the Aerosol Spatial Distribution and Relation with Clouds over Eastern China

ABSTRACTTo investigate the spectral and spatial distribution characteristics of aerosol particles over eastern China, this study conducted a set of aircraft measurements during August 12–28, 2014, over Anhui province, China. The aerosol number concentration and size distributions from five flights as well as the cloud and meteorological parameters were analyzed. In Anhui province, the average number concentration of aerosol particles in the size range of 0.1–3.0 µm was 481 ± 199 cm–3, and accumulation mode particles accounted for more than 95% of the total aerosol particles. Most of the aerosol particles were concentrated in the layer below 1000 m, where the number concentration decreased with the altitude, except in the presence of thermal inversion layers (TILs). The TILs prevented the vertical transport of aerosol particles, and led to a higher number concentration in the boundary layer. A large fraction of aerosol particles was removed when clouds were present, and the removed in-cloud aerosols lead to an increase in cloud droplet concentrations for the size range of 3.5–10.0 µm. Our results are valuable for understanding the spatial distribution of aerosol particles and their interactions with clouds.

Packing densification of binary cylindrical particle mixtures under 3D mechanical vibrations

The packing densification of binary cylindrical particle mixtures under 3D mechanical vibrations was systematically studied in physical experiments. The influences of vibration time, frequency, amplitude, vibration acceleration (vibration intensity), particle size ratio of large versus small particles, composition of the binary mixtures (volume fraction of large particles), and container size (wall effects) on the packing density of the binary cylindrical particles were discussed and analyzed. The results indicate that for each fixed composition and size ratio, high packing density can be obtained by properly controlling the vibration conditions. Appropriate composition (e.g. 72vol.%, volume fraction of large cylinders in current work) with large size ratio can contribute to the high packing density. Increasing the container size can reduce the container wall effects and obtain dense packing. Through extrapolation, the maximum packing density of binary cylindrical particles without container wall effects can reach about 0.8822, which agrees well with the proposed analytical model in literature.

Colloidal Mechanisms of Gold Nanoparticle Loss in Asymmetric Flow Field-Flow Fractionation.

Flow field-flow fractionation is a powerful method for the analysis of nanoparticle size distributions, but its widespread use has been hampered by large analyte losses, especially of metal nanoparticles. Here, we report on the colloidal mechanisms underlying the losses. We systematically studied gold nanoparticles (AuNPs) during asymmetrical flow field-flow fractionation (AF4) by systematic variation of the particle properties and the eluent composition. Recoveries of AuNPs (core diameter 12 nm) stabilized by citrate or polyethylene glycol (PEG) at different ionic strengths were determined. We used online UV-vis detection and off-line elementary analysis to follow particle losses during full analysis runs, runs without cross-flow, and runs with parts of the instrument bypassed. The combination allowed us to calculate relative and absolute analyte losses at different stages of the analytic protocol. We found different loss mechanisms depending on the ligand. Citrate-stabilized particles degraded during analysis and suffered large losses (up to 74%). PEG-stabilized particles had smaller relative losses at moderate ionic strengths (1-20%) that depended on PEG length. Long PEGs at higher ionic strengths (≥5 mM) caused particle loss due to bridging adsorption at the membrane. Bulk agglomeration was not a relevant loss mechanism at low ionic strengths ≤5 mM for any of the studied particles. An unexpectedly large fraction of particles was lost at tubing and other internal surfaces. We propose that the colloidal mechanisms observed here are relevant loss mechanisms in many particle analysis protocols and discuss strategies to avoid them.

Processing and consolidation of copper/tungsten

We developed a copper/tungsten (Cu/W) composite for mesoscale Materials Science applications using the novel High-Energy Diffraction Microscopy (HEDM) technique. Argon-atomized copper powder was selected as the starting raw powder and screened to remove the extremely large particle fraction. Tungsten particles were collected by milling and screening the −325 mesh tungsten powder between 500 and 635 mesh sieves. Hot pressing of screened Cu powder was performed at 900 °C in Ar/4 %H2 atmosphere. XRD and ICP results show that the hot-pressed Cu sample consists of about 5 vol% Cu2O, which is caused by the presence of oxygen on the surface of the starting Cu powder. Hot pressing the copper powder in a pure hydrogen atmosphere was successful in removing most of the surface oxygen. This process was also implemented for hot pressing the Cu/W composite. The density of the Cu/W composites hot pressed at 950 °C in pure hydrogen was about 94 % of the theoretical density (TD). The hot-pressed Cu/W composites were further hot isostatic pressed at 1050 °C in argon atmosphere, which results in 99.6 % of the TD with the designed Cu grain size and W particle distribution. Tensile specimens with D-notch were machined using the wire EDM method. The processing and consolidation of these materials will be discussed in detail. The HEDM images are also showed and discussed.

Investigating mixing and segregation using discrete element modelling (DEM) in the Freeman FT4 rheometer

Mixing and segregation in a Freeman FT4 powder rheometer, using binary mixtures with varied particle size ratio and volume fraction, were studied using the Discrete Element Method (DEM). As the blade moves within the particle bed, size induced segregations can occur via a sifting mechanism. A larger particle size ratio and/or a larger volume fraction of large particles lead to a quicker segregation process. A higher particle velocity magnitude can promote the segregation process and the rate for the segregation index increases in the radial direction: from the centre towards the outer layer. In the current DEM simulations, it is shown that the change in flow energy associated with segregation and mixing depends on the choice of frictional input parameters. FT4 is proposed as a potential tool to compare and rank the segregation tendency for particulate materials with distinct differences in flow energy of each component. This is achieved by measuring the flow energy gradient after a number of test cycles for mixing powders with different flow properties. Employing the FT4 dynamic powder characterisation can be advantageous to establish blending performances in an industrial context.

Grain growth jointly affected by immobile and mobile particles

Grain growth under the influence of randomly distributed particles is studied by numerical simulation using Onsager's principle. It was found that at small initial volume fraction of particles, normal grain growth evolves, with its kinetic law depending on the particle dissolution rate and its rate affected by particle mobility. At large initial volume fraction of particles, abnormal grain growth develops whereas an increase in particle mobility can lead to evolution of normal grain growth instead. Results of the simulations describe the effects behind some experimental data, lacking an explanation so far. They also allow improving existing and develop new technological solutions in the field of grain structure control and design.

Efficient neighbor list calculation for molecular simulation of colloidal systems using graphics processing units

We present an algorithm based on linear bounding volume hierarchies (LBVHs) for computing neighbor (Verlet) lists using graphics processing units (GPUs) for colloidal systems characterized by large size disparities. We compare this to a GPU implementation of the current state-of-the-art CPU algorithm based on stenciled cell lists. We report benchmarks for both neighbor list algorithms in a Lennard-Jones binary mixture with synthetic interaction range disparity and a realistic colloid solution. LBVHs outperformed the stenciled cell lists for systems with moderate or large size disparity and dilute or semidilute fractions of large particles, conditions typical of colloidal systems.

Gelation in mixtures of polymers and bidisperse colloids.

We investigated the effects of varying the volume fraction of large particles (r) on the linear rheology and microstructure of mixtures of polymers and bidisperse colloids, in which the ratio of the small and large particle diameters was α=0.31 or α=0.45. Suspensions formulated at a total volume fraction of ϕ_{T}=0.15 and a constant concentration of polymer in the free volume c/c^{*}≈0.7 contained solid-like gels for small r and fluids or fluids of clusters at large r. The solid-like rheology and microstructure of these suspensions changed little with r when r was small, and fluidized only when r>0.8. By contrast, dense suspensions with ϕ_{T}=0.40 and α=0.31 contained solid-like gels at all concentrations of large particles and exhibited only modest rheological and microstructural changes upon varying the volume fraction of large particles. These results suggest that the effect of particle-size dispersity on the properties of colloid-polymer mixtures are asymmetric in particle size and are most pronounced near a gelation boundary.