Standard Deviation Of Particle Size Research Articles

Self-organising phenomena in 2D complex plasma simulations withnon-mono dispersed dust size distributions

Complex plasma with a variety of continuous and discrete dust grain size distributions are simulated in 2D with molecular dynamics simulations with radial geometry to determine differences in self-organizing phenomena to more realistically represent the actual in situ variations in dust-size. The standard deviation of particle size σ(a) strongly correlates with phase separation and coupling parameter Γ for all distribution types. We observe local differences in bond order parameters and Voronoi diagrams for different size distributions, and our results suggest that phase transition is affected by continuous size distributions, particularly in the binary distribution case. Simulations with discrete size result in artifacts and discontinuities that are not found in the continuous distributions. The use of continuous distributions is observed to be beneficial both for more realistic approximation of complex plasma experiments and to study systems of strongly coupled particles in general.

Breakup process modeling and production of FeSiAl magnetic powders by close-coupled gas atomization

Close-coupled gas atomization is extensively used in the industrial production of alloy powders due to the advantages of high efficiency, low cost and excellent powder properties. In order to investigate the complex gas-liquid interaction during atomization, primary atomization was simulated through the VOF (Volume of Fluid) model and the dynamic adaptive mesh method, and a two-way coupling DPM (Discrete Particle Model) was used to simulate secondary atomization. The results showed that under the low melt mass flow rate of 0.0050 kg s−1, the flow separation and droplet backflow occurred at the atomization pressure of 1 MPa, while gas-liquid interfaces deformed and rotated drastically when the atomization pressure is above 3 MPa, which led to the formation of hollow powders. When the melt mass flow rate was 0.0150 kg s−1, the d50 decreased from 40.7 to 38.4 μm as the atomization pressure increased from 2 to 3 MPa. However, the chance of collision between particles increased due to the decrease in the spray cone angle, and both the standard deviation of particle size and atomization efficiency deteriorated, which indicated that 2 MPa was the optimum atomization pressure. As the mass flow rate increased from 0.0050 to 0.0150 kg s−1, the gas to melt ratio decreased, but the d50 only increased from 32.3 to 40.7 μm, indicating that the mass flow rate of 0.0150 kg s−1 did not significantly affect the particle size distribution, but also contributed to improve the production efficiency and avoided the risk of the nozzle freeze-off. The d50 of the spherical FeSiAl powders produced by the industrial tests at 2 MPa and 0.0150 kg s−1 was 44.7 ± 2.1 μm, which was basically consistent with the simulation results, indicating that the parameter optimization by the coupling model developed in this study could provide theoretical and practical guidance for the preparation of high-performance alloy powders by gas atomization.

Grain-size analysis of the Late Pleistocene sediments in the Corinth Rift: insights into strait-influenced hydrodynamics and provenance of an active rift basin

Abstract Grain-size analysis of the sediments in borehole M0079A, located in the Corinth Rift, was used to explore hydrodynamic conditions and provenance in the Late Pleistocene Corinth Rift. Grain-size populations that were sensitive to the sedimentary environments were characterized by frequency distribution, particle size–standard deviation and probability cumulative curves. Our results indicate the grain-size population component in the range 0.15–0.25 µm may be used as a sensitive proxy for hyperpycnal flows, which have commonly been triggered by river floods from the southern margin of the rift since c. 0.593–0.613 Ma. The high-density plumes derived from the longer rivers of the southern rift that were prevalent before c. 0.593–0.613 Ma. When sediment is supplied as hemipelagic deposition, the proportion of the total grain-size population that is in the 0.3–0.5 µm range becomes an index for suspension fall-out deposits. The core shows coarser sediments during the marine periods, and this may be linked to the current circulation related to the Ishtmia Strait opening. The study thus illustrates how the establishment of interbasinal straits can influence the details of sedimentary hydrodynamics in the deep-water axis of an adjacent depocentre.

Effects of Grinding Almond Hulls with a Hammermill on Particle Size and Bulk Density

The objective of this experiment was to evaluate the effects of grinding almond hulls with different screens on subsequent particle size and bulk density. Twenty pounds of almond hulls from the California Central Valley were ground with a laboratory-scale 1.5 HP Bliss Hammermill (Model 6K630B) using a 7/16 in., 3/4 in., 1 in., or no screen. Each screen size treatment was ground at three separate time points to provide three replications per treatment. For each replication, two samples were collected and analyzed for particle size geometric mean and standard deviation and bulk density. Geometric mean particle size was greater (P < 0.01) when no screen was used to grind almond hulls compared with 3/4-in. and 1-in. screens; moreover, particle size was decreased (P < 0.01) when ground with a 7/16 in. screen compared to all other treatments. Particle standard deviation did not differ (P = 0.13) between treatments. Bulk density of almond hulls tended to be greater (P = 0.07) when a 7/16-in. screen was used as compared to no screen, a 3/4-in. screen, and a 1-in. screen. Overall, unground almond hulls had a bulk density of 14.1 lb/ft3. Therefore, grinding almond hulls using a 7/16 in., 3/4 in., 1 in., or no screen led to an increase in their bulk density by 140, 115, 114, and 111%, respectively. Particle size was also evaluated using the Penn State Particle Separator. Grinding almond hulls with no screen tended (P < 0.01) to increase proportions of medium (i.e., 0.31 to 0.75 in.) particles and decrease (P ≤ 0.02) proportions of fine (i.e., < 0.16 in.) particles compared to grinding with a 7/16-in. screen. In conclusion, decreasing hammermill screen size reduced particle size from 2217 µm to 1324 µm but did not impact particle size standard deviation. In addition, grinding almond hulls increased bulk density by 111 to 140%. A live-bottom trailer with a load capacity of 2,835 ft3 could transport approximately 20 tons of unprocessed almond hulls. Conversely, the same trailer could transport 25 to 30 tons of ground almond hulls, thus, reducing transportation costs by 20 to 33% per ton, respectively.

Finite Element Investigation of the Influence of SiC Particle Distribution on Diamond Cutting of SiCp/Al Composites

Characteristics of internal microstructures have a strong impact on the properties of particulate reinforced metal composites. In the present work, we perform finite element simulations to elucidate fundamental mechanisms involved in the ultra-precision orthogonal cutting of aluminum-based silicon carbide composites (SiCp/Al), with an emphasis on the influence of particle distribution characteristic. The SiCp/Al composite with a particle volume fraction of 25 vol% and a mean particle size of 10 μm consists of randomly distributed polygon-shaped SiC particles, the elastic deformation and brittle failure of which are described by the brittle cracking model. Simulation results reveal that in addition to metal matrix tearing, cutting-induced particle deformation in terms of dislodging, debonding, and cracking plays an important role in the microscopic deformation and correlated machining force variation and machined surface integrity. It is found that the standard deviation of particle size to the mean value has a strong influence on the machinability of microscopic particle–tool edge interactions and macroscopically observed machining results. The present work provides a guideline for the rational synthesis of particulate-reinforced metal composites with high machinability.

Filter cake formation process by involving the influence of solid particle size distribution in drilling fluids

In the filter cake formation process (FCFP), existing models have assumed that the particles in drilling fluids are monosized, which is completely inconsistent with actual drilling fluids. Therefore, a novel FCFP prediction model was proposed by considering the solid particle size distribution (SPSD) and was verified using Hashemzadeh's model. The influences of SPSD, formation properties, drilling fluid properties, and engineering parameters on the FCFP were investigated. The results indicated that when the influence of SPSD is involved, the filter cake thickness is 2 times thicker than that of mean particle size; this means that the influence of SPSD on the FCFP cannot be ignored. The solid particle distribution type and mode in drilling fluids directly influence the FCFP. Adding the appropriate content of small-sized particles in drilling fluids will help form a high-quality filter cake. The filter cake growth rate increased with increasing in formation permeability, drilling fluid consistency coefficient, drilling fluid mobility index, pressure difference between the wellbore and formation; while it decreased with rising filtrate viscosity and drill-string rotational speed. The order of importance of influencing factors is mobility index > particle mean size > filtrate viscosity > particle size standard deviation > pressure difference > consistency coefficient > formation permeability > drill-string rotational speed. The present model can provide theoretical guidance for drilling fluid optimization, reservoir protection and well construction safety, thereby to facilitate safe, high-quality, efficient and economical drilling.

Continuous Synthesis of Highly Uniform Noble Metal Nanoparticles over Reduced Graphene Oxide Using Microreactor Technology

Batch reactors always suffer from inefficient transport properties, discontinuity, and scale-up effects, challenging the particle size control, reproducibility, and large-scale production of noble metal-reduced graphene oxide composites. To address these issues, a microfluidic-based strategy for the continuous synthesis of highly uniform Ag nanoparticles (NPs) over reduced graphene oxide (Ag-rGO composites) was developed in this study. Ag-rGO composites were formed by the coreduction of AgNO3 and GO with NaBH4, which was confined inside the dispersed aqueous plugs segmented by octane. By virtue of enhanced mixing and precise control of reaction parameters in the plugs, ultrafine Ag NPs with controlled particle size (1.5–5.6 nm) and narrow particle size distribution (PSD) were evenly deposited on rGO. The average particle size of Ag NPs and relative standard deviation of particle size in Ag-rGO composites synthesized via microfluidic-based strategy were smaller than those via batch method. Moreover, the versatility of this microfluidic-based strategy was further demonstrated in the continuous synthesis of Pt-rGO and Pd-rGO composites.

Improvement of the Graphene Oxide Dispersion Properties with the Use of TOPSIS Based Taguchi Application

The stability of the graphene oxide dispersions is an important issue in the preparation of medicine, printed flexible electronics, 3D printers and conductive inks. In order to improve the stability; mean and standard deviation of particle size, polydispersity index, zeta potential and conductivity of graphene oxide dispersion were selected as the main stability properties. The improvement rate between the estimate and the optimal conditions were calculated for the mean and standard deviation of particle size, polydispersity index, zeta potential and conductivity as 264.0%, 1875.0%, 583.3%, 5.0% and 50.0%, respectively in terms of the GO quality characteristics. The improvement rate between the estimate and the optimal conditions were calculated for the mean and standard deviation of particle size, polydispersity index, zeta potential and conductivity as 42.7%, 79.7%, -5.0%, 9.9% and -86.7%, respectively in terms of the GO quality characteristics. The result show that TOPSIS based Taguchi optimization in this study is effective to improve the graphene oxide dispersion stability.

Variation in aeolian environments recorded by the particle size distribution of lacustrine sediments in Ebinur Lake, northwest China.

Particle size analysis of lacustrine core sediments and atmospheric natural dust were conducted in the drainage area of Ebinur Lake in arid northwest China. Using a combination of 137Cs and 210Pb dating, a continuous record of aeolian transportation to the lake sediments and related factors over about the past 150 years was analyzed. Factor analysis revealed the particle-size distributions of riverine and aeolian sediments composed of the terrigenous materials of the lake deposits. Compared with the grain-size distributions of natural dust samples, the results showed that the coarser particle size fraction of lake sediments was mainly derived from the sediments that had experienced aeolian transport to the drainage surface, and the finer sediments came from hydraulic inputs. Then, the method of variations in particle-size standard deviation was used to extract the grain size intervals with the highest variability along a sedimentary sequence. The coarser grain-size populations dominated the variation patterns of the sedimentary sequence. During the last 150 years, strong intensity aeolian transportation occurred during three periods, 1915–1935, 1965–1975 and since the beginning of the 2000s. The climate was dry around 1910s–1930s in this region associated with the appropriate dynamic condition, which provided the enhanced source materials and wind power for the aeolian dust transport. Since 1950s, the climate controlled the foundation of aeolian dust transport, and the aeolian dust transport won’t be increased under the humid climate.

Flow Synthesis of Biocompatible Fe3O4 Nanoparticles: Insight into the Effects of Residence Time, Fluid Velocity, and Tube Reactor Dimension on Particle Size Distribution

PEGylated Fe3O4 nanoparticles were prepared through flow synthesis upon the pyrolysis of ferric acetylacetonate (Fe(acac)(3)) in anisole at 250 degrees C under pressure of 33 bar, in the presence of a,?-dicarboxyl-terminated polyethylene glycol (HOOC-PEG-COOH) and oleylamine. In combination with theoretical analysis, the effects of linear velocity, residence time, and reactor dimension on particle size distribution were systematically investigated. In addition, the impact of Ostwald ripening on particle size distribution was also revealed. In particular, the impacts of monomer concentration distributions along both axial and radial directions of the tube reactor on the particle size distribution were carefully investigated. Under optimized conditions, PEGylated Fe3O4 nanoparticles with the relative standard deviation of particle size down to 10.6% were thus obtained. The resulting 4.6 nm particles exhibited excellent colloidal stability and high longitudinal relaxivity (r(1)) up to 11.1 mM(-1) center dot s(-1), which manifested the reliability of flow synthesis in preparing PEGylated Fe3O4 nanoparticles as contrast agents for magnetic resonance imaging applications.

Synthesis of mono-disperse CoFe alloy nanoparticles with high activity toward NaBH4 hydrolysis

Traditionally, the synthesis of CoFe nanoparticles with tunable particle sizes and narrow particle size-distributions is accomplished via the use of expensive and air sensitive precursors and strong non-polar capping agents. Such strong capping agents can be difficult to remove from the nanoparticles and thus render them catalytically inactive. We report a novel solution-based methodology to synthesize CoFe alloy nanoparticles with narrow size-distributions using a combination of robust and inexpensive metal precursors and an easily removable polar capping agent. High resolution transmission electron microscope images show that the CoFe alloy nanoparticles are well crystallized, and the particle size is tunable from 9 to 24 nm while keeping a particle size standard deviation of 10%. The CoFe alloy nanoparticles show superior activity for NaBH4 hydrolysis compared with the best-known CoFe catalysts. This work represents a substantial improvement in the synthesis of transition metal nanoparticles, opening the pathway for their application to a number of technologically important catalytic applications.

A computational study of the role of particle size standard deviation on the collision frequency in differential settling

The results of a simple computational model for differential settling are presented illustrating the significant role that particle size distribution plays in collision frequency and sedimentation rate of particles in a quiescent environment. The model tracks a large number of particles (order 105) with log-normally distributed diameters, as they settle at their Stokes settling velocities. Particle collisions are detected and result in larger particles that fall more rapidly. A number of simplifying assumptions are made in the model in order to avoid empirical correlations for phenomena such as collision efficiency and particle shape. These simplifying assumptions were needed to isolate and quantify the role of the particle size distribution. Simulated concentration profiles indicate that, even in the absence of collisions, the standard deviation (σD) of the particle size strongly influences the bulk mass settling rate as, for larger σD, more mass is concentrated in larger, faster falling particles. The collision frequency is also a strong function of σD. For a given mass concentration the collision frequency first increases linearly with increasing σD as greater variation in particle size leads to greater variation in particle velocity, and shorter times for particles to catch each other. For larger σD more mass is concentrated in larger particles, so, for a given mass concentration, there are fewer particles per unit volume, increasing the mean distance between the particles and reducing the collision frequency. The implications of these results for sedimentation measurement using optical attenuation techniques are discussed.

기-고 유동층에서 Gaussian 분포 입자군의 표준편차에 따른 유출 특성

기-고 유동층에서 다입자경 입자의 입자분포 변화에 따른 비산유출 특성을 연구하였다. 다입자경 입자분포는 Gaussian 분포를 사용하여 실험을 수행하였다. 최소유동화속도에 대한 유속비와 Gaussian 입자분포의 표준편차에 따른 비산유출상수를 구하였으며, 이때 조업시간에 따른 압력요동의 특성치를 구하였다. 측정된 유동층의 압력요동 특성치로부터 압력요동의 표준편차, 평균압력, Power spectrum density function, 주진동수 등을 계산하였다. 입자분포군에 따라서 유출입자의 입자분포 및 압력요동 특성치는 크게 영향을 받는 것으로 나타났으며 이러한 결과로부터 압력요동 특성치로부터 유출특성의 해석이 가능함을 알 수 있었다. The elutriation characteristics of particle size distribution were investigated in a gas-solid fluidized bed. Experiments were carried out with the mulit-sized particles of Gaussian distributions. The elutriation rate constant obtained from the experiment was correlated with the standard deviation of particle size and the dimensionless group of the velocity ratio. The standard deviation of pressure fluctuation, mean pressure, major frequency and power spectrum density function were calculated by pressure fluctuation properties. Size distribution of elutriated particles and pressure fluctuations were measured for the particle size distribution of particle system depended largrly on the size distribution. Characteristics of fluidization and elutriation were greatly influenced by the particle size distribution and these characteristics could be interpreted with pressure fluctuation properties.

Mass production of cathode materials for lithium ion battery by flame type spray pyrolysis

Lithium transition metal oxide cathode materials such as LiAl0.05Mn1.95O4, LiNi0.5Mn1.5O4, LiCo1/3Ni1/3Mn1/3O2 were successfully produced at a rate of 2 kg/h by large flame type spray pyrolysis. The continuous spray pyrolysis of 250 h exhibited the good stability for powder production. The powder characteristics of them were determined by SEM, XRD, BET and AAS. Cathode materials had spherical morphology with a particle size of about 8 μm and porous microstructure with specific surface area of 10 m2/g. Their geometrical standard deviation of particle size ranged from 1.2 to 1.5. The chemical composition of them was in good agreement with that of the starting solution. The electrochemical measurement revealed that these cathode materials exhibited the higher rechargeable capacity, good cycle performance and thermal stability.

Preface: phys. stat. sol. (b) 245/3

Preface: phys. stat. sol. (b) 245/3

HABITAT USE AND BEHAVIOR OF THE PACIFIC SAND LANCE (AMMODYTES HEXAPTERUS) IN THE SHALLOW SUBTIDAL REGION OF SOUTHWESTERN VANCOUVER ISLAND

The Pacific Sand Lance (Ammodytes hexapterus) is an important Pacific Northwest prey species for marine predators. In our study along the West Coast Trail, southwestern Vancouver Island, British Columbia, we examined shallow subtidal habitat selection of juvenile and adult Sand Lance with respect to sediment characteristics, and also examined aggregation behavior. Analysis of presence or absence using a classification tree showed that Sand Lance avoided sites with no subtidal sediments, preferred sites with mean sediment particle sizes ≤ 1290 μm and preferred mixed sediments (sorting values >3.09 standard deviations; standard deviation of particle size used as a heterogeneity index of the substrate grain size). The regression tree analysis explained 99% of the variation in abundance based on the effects of mean particle size, particle sorting and presence or absence of sediments, but the model showed evidence of over-classification due to small sample sizes. Nevertheless, the model indicated environmental factors that are important for Sand Lance habitat use. Behavioral analysis showed that Sand Lance aggregated into larger schools to feed and these schools tended to occur in the mid-water column compared to non-feeding schools which remained closer to the seafloor. Near the beaches, 0-year (young-of-the-year) Sand Lance were found in deeper water compared to older Sand Lance (1 -year classes). Together these data suggest that Sand Lance using the shallow subtidal show some indication of habitat use based on particle size and sorting, and aggregation differences based on behavior and age class.

Novel Technique for Fabrication of Nanoparticle Structures in KNbO3–TeO2 Glass for Photonic Integrated Circuits

We succeeded in fabricating novel nanoparticle structures on KNbO3–TeO2 glass induced by ultraviolet (UV) laser irradiation and found that the size and size distribution could be controlled by the conditions of laser irradiation, such as fluence, pulse repetition rate, and the temperature of the glass specimen by heat assistance (HA). Nano-sized particles are an interesting new material, because they will be able to open the door to the invention of photonic circuits of extremely small size, which transfer optical signals through optical near-field energy operating by a completely different principle. The particle diameters may be controlled from approximately 200 nm up to 500 nm by modifications of UV laser fluence and the repetition rate of pulses. When using HA with a glass specimen during laser irradiation, it has been found that nanoparticle formation is activated and particle size increased as the temperature of the glass increased, and the uniformity of particle size is markedly improved by HA treatment. The standard deviation of particle size is 20 nm at 100 °C. A 60% improvement in the size variation of particles is possible in comparison with laser irradiation without HA. These results suggest that heat is involved in nanoparticle formation during UV laser irradiation, which means that the overall history of heating with pulsed laser irradiation is critically important to control the form of the particles. Furthermore, periodic structures with an 800 nm pitch constructed by lines of ordered nanoparticles with diameters of approximately 150–300 nm were successfully fabricated by laser irradiation through a phase mask. This is a significant advancement towards the realization of nanophotonic circuits.

Particle Size, Mill Type, and Added Fat Influence Angle of Repose of Ground Corn

Three experiments were conducted to determine the effects of particle size (PS), mill type (MT), and added fat on flow characteristics of ground corn. In Exp. 1, PS of samples ground with a roller mill (RM) ranged from 1,235 to 502 µm; samples ground with a hammermill (HM) ranged from 980 to 390 µm. Soy oil was added at 0, 2, 4, 6, and 8% to each sample. Flow ability was determined by measuring angle of repose. A PS × fat × MT interaction (P < 0.05) was observed. As PS decreased and fat increased, the differences in angle of repose between HM-and RM-grain ground decreased. Corn ground with a HM without fat had a similar angle of repose to RM-ground corn with 6% fat. In Exp. 2 and 3, RM- and HM-ground corn were sifted through a stack of 13 screens and material on top of each screen was collected. In Exp. 2, mean PS of RM samples selected from different individual screens ranged from 1,415 to 343 µm and of HM samples ranged from 1,382 to 333 µm; all samples had similar particle size standard deviation (PSSD; 1.1 to 1.3). A PS × fat × MT interaction (P < 0.05) was observed. In fine ground HM samples, differences in flow ability between amounts of fat decreased as PS decreased, whereas in RM samples the differences were maintained. In Exp. 3, RM and HM samples were constructed to have a similar PS (641 to 679 µm) with increasing PSSD (1.62 to 2.27). Increasing fat (P < 0.04) and PSSD (P < 0.001) decreased flow ability. These results suggest that the greater flow ability of RM ground corn is a result of decreased PS variation compared to that of HM ground corn.

Comparison of particle size analysis of ground grain with, or without, the use of a flow agent (2006)

Summary The American Society of Biological and Agricultural Engineers’ standard for particle size analysis indicates that the analysis can be conducted with or without the use of a flow agent. Because of this allowed variation in procedures, particle size analysis results can be variable and difficult to interpret, depending on whether the laboratory uses a flow agent or not. Therefore, a retrospective analysis was made of 603 samples of ground corn analyzed for particle size with, or without, 0.5 g of synthetic amorphous precipitated silica (Sipernat® 22-S) per 100 g of sample. Results of both analyses were compared with a Method of Agreement analysis. Results indicated that there was a bias between the two procedures for particle size analysis, but that the bias was consistent across the range of particle sizes evaluated (400 to 1000 µ). Particle size analysis conducted with a flow agent will result in a mean particle size that is approximately 80 µ smaller than the result from analysis without a flow agent. The same procedures were used in comparison of particle size standard deviation. Using a flow agent produced a greater particle size standard deviation value than without a flow agent. Unlike the bias for the particle size analysis, which was consistent for the wide range of samples evaluated, the standard deviation values showed a significant bias. As the standard deviation of the sample increased, the magnitude of difference between the two procedures also became greater. Results of this study indicate that there are differences in results between the two procedures; therefore, selection of one of the two procedures as the official standard is necessary. Also, it is important to know if a flow agent was, or was not, used in the analysis when interpreting results.

Photoluminescence of ZnO Nanoparticles Prepared by Laser Ablation in Different Surfactant Solutions

ZnO nanoparticles were prepared by laser ablation of a zinc metal plate in a liquid environment using different surfactant (cationic, anionic, amphoteric, and nonionic) solutions. The nanoparticles were obtained in deionized water and in all surfactant solutions except the anionic surfactant solution. The average particle size and the standard deviation of particle size decreased with increasing amphoteric and nonionic surfactant concentrations. With the increase of the amphoteric surfactant concentration, the intensity of the defect emission caused by oxygen vacancies of ZnO rapidly decreased, while the exciton emission intensity increased. This indicates that anionic oxygen in the amphoteric surfactant molecules effectively occupied the oxygen vacancy sites at the ZnO nanoparticle surface due to charge matching with the positively charged ZnO nanoparticles.